Tuning Logic of Imidazole Heteroaromatic Building Blocks: How Dual Nitrogen Sites and Substitution / Salt Forms / Ring Fusion Modulate Charge, Hydrogen Bonding, and Coordination (with Tables A–E)

1.Real-World Problem: Why Can the Same Molecule Behave Very Differently with pH or Metal Ions?

In drug molecules, catalytic systems, separation/purification, and materials media, R&D often encounters a recurring challenge: the same molecule shows dramatically different behavior under different conditions, making results difficult to reproduce. Typical triggers fall into three main categories:

1. Small changes in pH can shift the distribution of ionic states (especially when pH is close to the key site’s pKa), which in turn affects solubility, adsorption/binding strength, and reaction rate.

2. Metal ions in the system (transition metals such as Fe/Cu/Zn/Ni—even at trace levels) may coordinate/chelate with the molecule, generating new structural states and reaction pathways.

3. Different substituents or different salt forms / counterions on the same core scaffold can change charge distribution and solvation, making an originally broad “effective window” much more sensitive.

A key reason imidazole-type heteroaromatic building blocks have remained high-frequency motifs for decades is this: a small, clearly defined aromatic five-membered ring concentrates these differences into a few core, comparable factors—charge state (acid–base), hydrogen-bond networks, and metal-coordination ability—making systematic comparison and targeted tuning easier.

2.Basic Concepts: What Are “Heteroaromatic Building Blocks—Imidazole Family”?

2.1 Heteroaromatic building blocks

Here, a “building block” refers to a ring module that can be repeatedly used in molecular design. It can be used to build scaffolds, tune polarity and electronic effects, provide key interaction sites, and support series-based iteration (clear structural controls; property changes are easier to interpret). Emphasizing “building block” highlights that it is more like a standardized, reusable modular interface, rather than a one-off intermediate or a temporary functional group.

2.2 Imidazole and the imidazole family

1. Imidazole: an aromatic five-membered heterocycle with two nitrogens (a 1,3-diaza ring). It exhibits 1H/3H tautomerism, and is commonly described using 1H-imidazole as the main representation. In any given tautomer, it presents a combination of one pyridine-like N (primarily a hydrogen-bond acceptor; more often involved in coordination; more readily protonated) plus one pyrrole-like N–H (linked to aromaticity; more often acting as a hydrogen-bond donor).

For unsubstituted imidazole, tautomerism interconverts the two forms, so the “pyridine-like / pyrrole-like roles” of the two nitrogens are interchangeable on average (not permanently fixed on the same nitrogen). Imidazole and its protonated form imidazolium form a conjugate acid–base pair.

2. Imidazole family: a group of structure types centered on the imidazole ring that are most often treated as reusable building blocks in R&D. Common examples include:

a) Imidazole core and substituted imidazoles (for tuning acid–base properties, hydrogen bonding, and the solubility/salt-form window);

b) Fused-ring derivatives (e.g., benzimidazole, often used as medicinal chemistry scaffold platforms);

c) Imidazolium salts (stable ionic forms, often used as an “ionic-state entry / precursor”);

d) N-heterocyclic carbene (NHC) ligand systems derived from imidazolium salts (carbenes generated by deprotonation at the key carbon, used to build coordination and catalytic systems).

2.3 A common natural reference: the imidazole side chain of histidine

Histidine’s side chain contains an imidazole ring. Literature often gives an “empirical range”: the pKa of the imidazole side chain is frequently around ~6. This means that within a pH window such as 5.5–6.5, it more readily displays switchable charge states (protonated/deprotonated), thereby providing some buffering capacity while strongly influencing hydrogen bonding, electrostatics, and metal coordination.

Additional note: this pKa is not a fixed constant—it can shift with microenvironment (ionic strength, nearby charges, local structure/hydrophobicity, etc.). Even so, “near physiological pH and readily switching between two states” remains one important reason imidazole is used so frequently in biological systems.

3.Structural Features: Four Key “Property Switches” of Imidazole

The “information density” of imidazole comes from the non-equivalence of its two nitrogens:

1. Pyrrole-like N–H: its lone pair participates in aromaticity; it behaves more as a hydrogen-bond donor.

2. Pyridine-like N: its lone pair does not participate in aromaticity; it is the primary hydrogen-bond acceptor and more often serves as a metal-coordination site.

Together with tautomerism (N–H position switching), protonation / salt formation (imidazolium), and the very common ring-fusion expansion (benzimidazole, etc.), most experimentally observed property changes can be explained with the following four “switches”:

Structural switch (what is changed)	What it changes (core reason)	Common observable outcomes
Division of labor between the two nitrogens (N–H vs N:)	In the neutral state, it often appears as “one N–H donor + one N acceptor”; the nitrogen bearing a lone pair (pyridine-like N) more often participates in metal coordination and is more readily protonated.	Richer H-bond/binding modes; more sensitive to solvent, salts, and metal ions; the same scaffold shows larger differences across different systems.
Tautomerism (N–H migrates between the two nitrogens)	Donor/acceptor positions can switch; electron distribution and H-bond geometry change accordingly.	More than one interaction/binding orientation may exist; behavior can be “less single-state” (e.g., broadened spectra / multiple sets of signals; multimodal binding data).
Protonation / salt formation (imidazole → imidazolium)	Charge state strongly changes polarity and ionic interactions; H-bond acceptor ability is markedly weakened or lost.	Clear “switch-like” changes in solubility, partitioning/adsorption, and interfacial behavior; more sensitive to counterion and ionic strength.
Ring fusion expansion (e.g., benzimidazole)	Increased rigidity and π-system size; higher contribution of hydrophobic and π–π interactions; often accompanied by shifts in acid–base behavior and solubility window.	Better suited for series-based comparisons (affinity/selectivity trends more comparable); but may reduce solubility or increase nonspecific adsorption; metabolic/chemical stability trends often shift with scaffold rigidity.

4.Practical Classification of the Imidazole Family: What You Change → What Shifts → Why It’s Commonly Used

Category	Typical structural modification	Main properties being tuned	Common use cases
A. Core / lightly substituted imidazoles (baseline controls)	Unsubstituted or minimally substituted; closest to “origin behavior”	Baseline of acid–base behavior + H-bond donor/acceptor pattern + coordination ability	Most direct system baseline/control; quickly tests whether “imidazole fits this system.”
B. N-substituted imidazoles (remove N–H, reduce multi-state behavior)	Alkyl/aryl substitution at N (reduces or eliminates N–H)	Tautomerism greatly reduced; H-bond donor ability decreases/disappears; protonation, salt formation, and solubility behavior shift accordingly	More single-state and easier to reproduce; preferred when N–H would introduce extra H-bonds/multiple forms; also used as a more controllable coordination/polarity module.
C. C-substituted imidazoles (2/4/5 fine-tuning and “handles”)	Substituents or linkers introduced at 2/4/5 positions	Integrated tuning of electronic effects + sterics + polarity/hydrophobicity; often affects pKa, solubility, and the spatial position/orientation of interactions (H-bond angles, coordination geometry, etc.)	Fine-tuning binding strength/selectivity; the 2-position is often used as a “linking handle” for series-based controls (turning substituent changes into a controllable SAR gradient).
D. Ring fusion expansion: benzimidazoles, etc. (more rigid, more π-biased)	Fusion of imidazole with an aromatic ring; expanded π system and greater rigidity	Rigidity ↑; weight of π/hydrophobic interactions ↑; often accompanied by shifts in acid–base and solubility windows	Often discussed as drug scaffolds/fragment platforms: facilitates series-based comparisons and property transfer; requires attention to solubility vs nonspecific adsorption trade-offs.
E. Ionic state: imidazolium salts (charge-state switch)	Positively charged imidazolium with different counterions	Ionic interactions, dielectric/solvation, and interfacial behavior change markedly; counterion effects are often large	Common in ionic liquids/electrolytes and functional materials; key entry point for NHC precursors; more direct when a “positively charged model” or strong ionic interactions are needed.

5.Three Application Mainlines

Application mainline	Structural categories mainly used (corresponding to Part 4 A–E)	Key benefits brought by structural change	What to prioritize measuring
Drugs / bioactive molecules	H-bond donors/acceptors + a tunable protonation window (mainly A/C/D)	The same scaffold can turn “H-bond geometry, polarity, and charge state” into iteratable SAR variables via substitution / ring fusion	Whether the binding mode is stable; salt form / solubility window; activity/selectivity trends driven by substitution position changes
IMAC purification (His-tag)	Coordination competition (A is the most typical)	Turns “metal coordination” from a nuisance into a process knob: imidazole competes with immobilized metal sites, enabling controllable wash/elution windows	In washing: whether nonspecific binding decreases; in elution: whether the target elutes cleaner/more concentrated; process signals such as metal leaching and protein recovery yield
Catalysis and functional media	Ionic state / imidazolium (E) and derivatives	Imidazolium is both a common entry point to NHC (N-heterocyclic carbene) precursors and a modular unit for “tunable media” (ionic liquids/electrolytes); structure and anion/cation pairing directly determine system properties	In catalysis: mapping activity/selectivity to ligand electronics/sterics; in media: viscosity/polarity/solubility/phase behavior responses to cation–anion combinations

Application Quick Reference: Three Most Typical “Structure → Use” Implementation Paths

1. Drugs / bioactive molecules (e.g., benzimidazoles)

a) Use the same scaffold to couple H-bond donor/acceptor features with a protonation / salt-forming window, then perform series-based fine tuning through substitution / ring fusion.

b) How to use: treat binding mode + solubility/salt form + selectivity as an iteratable set of SAR variables for side-by-side comparison.

2. His-tag protein IMAC (Immobilized Metal Affinity Chromatography) purification

a) Exploit imidazole’s coordination competition: low concentrations for washing to reduce nonspecific adsorption; high concentrations for eluting the target protein.

b) How to use: treat imidazole concentration as a process knob; optimize the window around “wash background/purity—recovery—elution peak shape.”

3. Imidazolium salts (Category E): catalysis and functional media

a) As a charge-state platform, one end serves catalysis control as a common precursor entry to NHC ligands; the other end enables tunable media in ionic liquids/electrolytes via “cation substitution + anion/counterion selection.”

b) How to use: when strong ionic interactions or tunable medium properties are needed, prioritize selecting an “imidazolium platform” and treat the counterion as a key variable for side-by-side comparison. Also note that systems containing BF₄⁻/PF₆⁻ may undergo anion hydrolysis under aqueous or acidic conditions and introduce corrosion risk (HF). In electrolytes/surface treatment/aqueous systems, include water content / acidity and materials compatibility as explicit evaluation variables.

6.Product Navigation Table | Selection for “Imidazole / Benzimidazole Systems”: Quickly Locate Tables A–E by R&D Task

Your research task / experimental need	Recommended table to check first	Selection logic
Gastric acid–related research / quality analysis: PPI reference standards (omeprazole/esomeprazole/lansoprazole/pantoprazole/rabeprazole)	Table A	Within one pharmacological family, “horizontal comparisons” are often needed (stability, impurity profile, salt form/polymorphs, method validation). Putting them in one table minimizes lookup cost.
H2-receptor pharmacology / receptor binding & reference (cimetidine)	Table A	H2 antagonists and PPIs differ mechanistically, but both fall under “gastric acid–related drug reference” scenarios; Table A centralizes them for one-click locating.
Anti-anaerobic / antiprotozoal: nitroimidazole API references (metronidazole/tinidazole/secnidazole/ornidazole)	Table B	Nitroimidazoles form a highly homologous compound group; commonly used for efficacy/tolerability/PK comparisons and analytical method development—fastest to search when centralized in Table B.
Antifungal drug research / references / impurities & stability: azole antifungals (clotrimazole/miconazole/econazole/oxiconazole/bifonazole/tioconazole/ketoconazole/fluconazole nitrate)	Table C	Strong shared features (solubility/formulation window, methods, impurity profiles); within-table side-by-side comparison is most practical.
Agrochemical fungicide activity / references / methods: benzimidazole fungicides (thiabendazole/carbendazim/benzimidazole carbamates)	Table C	Different from pharma azoles, but still a “fungal control” application set; Table C groups by use to enable quick locating and comparisons.
“Imidazole / benzimidazole” heteroaromatic building blocks: need cores and substituted variants for structure controls	Table D	Focus is on “entry structures / derivatizable positions,” not pharmacology; Table D groups by building blocks and tools, matching synthesis-driven selection.
Functionalization handles: 2-amino / 2-halo / arylation / nitro substitution (for subsequent coupling, substitution, or SAR expansion)	Table D	Value lies in “what structure you can modify next”; Table D centralizes these for selecting starting materials by reaction handle.
MOF/ZIF materials: need 2-methylimidazole (2-MeIm) as a high-frequency ligand	Table D	2-MeIm is frequently used in ZIF synthesis and should be located as a “materials ligand / foundational building block”; Table D is the most direct.
Metal corrosion inhibition / anti-tarnish / metal-coordination additives: thio-imidazoles/benzimidazoles (2-mercaptoimidazole, 2-mercaptobenzimidazole, 2-mercapto-1-methylimidazole)	Table D	Core is N/S dual-site adsorption/coordination on metal surfaces; this is an engineering/material additive route and is centrally collected in Table D.
Carboxylic acid → amide/ester/carbonate coupling: need CDI (N,N′-carbonyldiimidazole)	Table D	CDI is a classic “imidazole activation” coupling tool; it is categorized by reagent function in Table D for parallel screening vs similar activators.
Sulfonylation / sulfonamide synthesis: need 1,1′-sulfonyldiimidazole	Table D	A sulfonylation activator; best retrieved as a “synthetic tool,” and Table D provides direct locating for route comparison.
Dicarbonyl activation / route-development controls: need 1,1′-oxalyldiimidazole (oxalyl diimidazole)	Table D	Same “imidazole activation” concept as CDI but with a different reactivity window; Table D enables process window/side-reaction comparisons.
Primary amine → organic azide diazotransfer: 1H-imidazole-1-sulfonyl azide hydrochloride	Table D	A typical diazotransfer reagent; selection prioritizes use case and controllability/safety boundaries. Evaluate and handle under organic azide safety norms; avoid treating it as a generic azide source.
Ionic liquids as solvents/electrolytes/separation media: EMIM/BMIM + BF₄⁻/PF₆⁻/TFSI⁻/Cl⁻	Table E	The main variables are “cation scaffold + anion switching”; Table E allows direct comparison of viscosity/polarity/phase behavior/electrochemical window by platform.
Ionic liquid synthesis precursors / anion-exchange routes: imidazolium chloride salts such as EMIMCl, BMIMCl	Table E	Chloride salts are common ionic-liquid precursors (then swapped to BF₄⁻/PF₆⁻/TFSI⁻). Table E is organized by “precursor → platform,” matching the process pathway.
NHC metal catalysis: bulky aryl imidazolium salts (Mes / IPr types) as NHC precursors	Table E	Focus is ligand sterics/electronics and catalytic stability; this is “ligand-precursor platform” selection, centralized in Table E for direct picking.
Need N-alkyl imidazoles as bases / ligands / ionic-liquid precursors (1-ethyl/1-butyl, etc.)	Table E	These molecules often switch among three roles (base/ligand/ionic-liquid precursor); Table E unifies them to avoid fragmented lookup.
Biochemistry / cell culture or physiological references: L-histidine, histamine	Table D	These are biological inputs/references and should not be mixed with drug APIs or ionic liquids; Table D groups them more clearly by “basic molecules and use.”

Table A | Pharmaceutical APIs | Acid Suppression & Gastric Drugs (PPIs + H2)

Category	CAS No.	Aladdin Cat. No.	Name	Specification / Purity	Product features & applications
Pharmaceutical API | PPI acid suppressant	119141-88-7	S586538	Esomeprazole	Moligand™, ≥99%	Representative proton pump inhibitor (PPI): used in gastric acid–related disease research; reference standard for impurity profiling and stability studies; suitable for “PPI series horizontal comparisons” (vs omeprazole, etc.) to evaluate how configuration/salt form affects properties.
Pharmaceutical API | PPI acid suppressant	73590-58-6	O118724	Omeprazole	Moligand™, ≥98%	Classic PPI reference: used for gastric acid drug research, reference standards, impurity profiling, and stability studies; also a representative case for “PPIs as acid-labile prodrugs,” highlighting formulation and storage considerations.
Pharmaceutical API | PPI acid suppressant	103577-45-3	L129650	Lansoprazole	Moligand™, ≥98%	PPI series member: used for drug research, reference standards, and stability/impurity studies; suitable for cross-comparison with omeprazole/pantoprazole/rabeprazole to link “structural differences → property/metabolism differences.”
Pharmaceutical API | PPI acid suppressant	102625-70-7	P302094	Pantoprazole	Moligand™, ≥97%	PPI series member: used for API research and analytical references; often used to compare PPIs in stability, salt form/polymorph behavior, and process windows.
Pharmaceutical API | PPI acid suppressant	117976-89-3	H172338	Rabeprazole	Moligand™, ≥97%	PPI series member: used for drug research, reference standards, and method/stability studies; suitable for comparative analysis of “fine structural tuning → PK/stability differences” vs other PPIs.
Pharmaceutical API | H2 receptor antagonist (imidazole-containing)	51481-61-9	C102301	Cimetidine	Moligand™, ≥99%	Classic H2 receptor antagonist: a representative receptor ligand containing an imidazole ring, used for pharmacology research, analytical references, and interaction studies; also commonly cited to discuss how imidazole basicity/coordination affects in vivo and in vitro behavior.

Table B | Pharmaceutical APIs | Nitroimidazoles (Anti-anaerobic / Antiprotozoal)

Category	CAS No.	Aladdin Cat. No.	Name	Specification / Purity	Product features & applications
Pharmaceutical API | Nitroimidazole (anti-anaerobic / antiprotozoal)	443-48-1	M432726	Metronidazole	UltraBio™, Ultra-pure grade	A representative nitroimidazole anti-anaerobic/antiprotozoal drug: used in drug research, analytical reference work, and impurity/degradation studies; the “nitroimidazole” motif is also a widely used representative in studies of anti-anaerobic activity and bioreductive mechanisms.
Pharmaceutical API | Nitroimidazole (anti-anaerobic / antiprotozoal)	19387-91-8	T162647	Tinidazole	Moligand™, ≥98% (HPLC) (T)	A representative nitroimidazole: used for API research and reference comparisons in anti-anaerobic/antiprotozoal applications; often compared with metronidazole as a reference set for “efficacy—tolerability—dosing” trade-offs.
Pharmaceutical API | Nitroimidazole (anti-anaerobic / antiprotozoal)	3366-95-8	S129270	Secnidazole	≥98%	A representative nitroimidazole: used for drug research and reference standards; commonly considered alongside metronidazole/tinidazole/ornidazole for “within-class structural differences → course length / tolerability / pharmacokinetics” comparisons and for analytical method validation.
Pharmaceutical API | Nitroimidazole (anti-anaerobic / antiprotozoal)	16773-42-5	O129376	Ornidazole	≥98%	A nitroimidazole API: used in anti-anaerobic/antiprotozoal research, reference standards, and quality analysis; also applicable to studies of nitro-reduction mechanisms and resistance.

Table C | Pharmaceutical / Agrochemical | Azole Antifungals + Benzimidazole Fungicides

Category	CAS No.	Aladdin Cat. No.	Name	Specification / Purity	Product features & applications
Pharmaceutical API | Azole antifungal (imidazole)	65277-42-1	K475027	Ketoconazole	Moligand™, ≥99% (EP, titration)	Broad-spectrum imidazole antifungal: used for API research, QC, and method validation; a representative example of the “azole ring–coordination” mechanism (inhibition of fungal CYP51), widely referenced in azole SAR and resistance studies.
Pharmaceutical API | Azole antifungal (imidazole)	23593-75-1	C129965	Clotrimazole	Moligand™, ≥98% (HPLC)	Classic imidazole antifungal: commonly used in topical formulation research, analytical references, and method development; also a representative case highlighting that many azoles are highly hydrophobic and require careful management of formulation/solubility windows.
Pharmaceutical API | Azole antifungal (imidazole)	22916-47-8	M303130	Miconazole	Moligand™, ≥98%	Imidazole antifungal: often used in topical/local formulation studies, reference standards, and quality analysis; also useful for studying common features of “azole–metalloenzyme target interactions.”
Pharmaceutical API | Azole antifungal (imidazole)	27220-47-9	E355746	Econazole	Moligand™, ≥97%	Imidazole antifungal: used for drug research, analytical references, and related formulation/impurity studies; commonly used as a reference sample in topical antifungal drug systems.
Pharmaceutical API | Azole antifungal (imidazole)	60628-96-8	B129316	Bifonazole	≥98% (HPLC)	Topical imidazole antifungal: commonly used in formulation/solubility-window and quality-analysis studies; can serve as a reference sample for “highly hydrophobic azoles” in formulation and delivery-system comparisons.
Pharmaceutical API | Azole antifungal (imidazole)	65899-73-2	T304306	Tioconazole	≥98%	Imidazole antifungal: used for API research, analytical references, and impurity/stability studies; since solubility and formulation-window management is a shared feature of azoles, it is suitable for method and formulation benchmarking.
Pharmaceutical API | Azole antifungal (imidazole)	64211-45-6	O355745	Oxiconazole	≥97%	Topical imidazole antifungal: used for API research, analytical references, and formulation/stability studies; suitable for within-class comparisons with miconazole/econazole and related agents.
Pharmaceutical API | Azole antifungal (imidazole, salt form)	61318-91-0	S129489	Sulconazole nitrate	≥95%	Salt-form azole antifungal: used for API/reference standards and analytical method development; salt forms may improve stability/handling or support formulation-window assessment, making it suitable as a “free base vs salt form” comparison sample.
Pesticide / fungicide | Benzimidazole class (fungal control)	148-79-8	T276605	Thiabendazole	≥99%	Representative benzimidazole fungicide: used in agrochemical activity studies, reference standards, and method development; also a common sample for studying benzimidazole–fungal target interactions and resistance issues.
Pesticide / fungicide | Benzimidazole class (carbendazim)	10605-21-7	C140191	Carbendazim	≥97%	Classic systemic benzimidazole fungicide: used for agrochemical activity research, reference standards, and method development; also a common representative in “activity—resistance” discussions of the benzimidazole class.
Pesticide / fungicide | Benzimidazole class (systemic fungicide)	17804-35-2	B197283	1-Butylcarbamoyl-2-benzimidazolyl methylcarbamate	≥97%	A benzimidazole carbamate-type fungicide structure: used for agrochemical activity/mechanism studies and analytical references; also used in impurity profiling, degradation studies, and method development.

Table D | Core Scaffolds / Derivatives / Functional Monomers + Synthetic Reagents (Grouped by “Similar Structure and Use”)

Category	CAS No.	Aladdin Cat. No.	Name	Specification / Purity	Product features & applications
Biochemical amino acid | Histidine platform (cell culture / coordination site)	71-00-1	H108261	L-Histidine	Animal-free, USP, Moligand™, European Pharmacopoeia (Ph. Eur.), for cell culture	A key amino acid bearing an imidazole side chain: commonly used nutrient component and reference in cell culture/biochemical systems; the imidazole site can participate in metal coordination and acid–base control, supporting protein/enzyme studies, metal-binding behavior investigations, and buffer-related experiments.
Biogenic amine | Histamine (receptor ligand / physiological activity reference)	51-45-6	H111796	Histamine	Moligand™, ≥96%	An endogenous biogenic amine containing an imidazole ring: commonly used in H1/H2 receptor pharmacology, allergy/inflammation model references, and method validation; also a classic example of how “imidazole basicity/protonation state” manifests in biological systems.
Core scaffold | Imidazole (general buffer / coordination / catalysis)	288-32-4	I432539	Imidazole	Anhydrous grade, ACS, ≥99%	Classic imidazole core: widely used for buffering and pH control (e.g., biochemical/protein systems), and as a competitive eluent in His-tag protein purification; also used as an N-donor ligand/intermediate and as a nucleophilic catalyst (acylation/condensation, etc.), serving as a starting point for many imidazole/imidazolium derivatives.
Salt form | Imidazole salt (acidified solubility / coordination & buffering)	1467-16-9	I120637	Imidazole hydrochloride	≥98%	Salt-form control of imidazole: used to increase water solubility and establish systems with more controllable acidity/ionic strength; also commonly used to compare “free base vs salt form” in coordination/buffering-related experiments.
Core scaffold | Benzimidazole (heteroaromatic building block / coordination platform)	51-17-2	B106095	Benzimidazole (BZI)	AR, ≥98% (HPLC)	Classic benzimidazole core: widely used building block in drug and materials chemistry; can form salts to tune solubility; also serves as an N-donor coordination/H-bond scaffold for ligand design, functional materials, and building-block library construction.
Benzimidazole derivative | N-substituted building block / coordination & materials precursor	1632-83-3	M110306	1-Methylbenzimidazole	≥99%	An N-substituted benzimidazole building block: used for building-block libraries and further functionalization; also serves as an N-donor ligand/ion-pair model and as a starting point for metal coordination and materials-related studies.
Benzimidazole derivative | 2-methyl substitution (building block / coordination)	615-15-6	M110232	2-Methylbenzimidazole	≥98%	Common benzimidazole building block: for building salt-formable/coordination-capable fragment libraries; 2-substitution helps tune basicity, solubility, and H-bonding patterns, suitable for SAR/material control comparisons.
Biochemistry-related | 5,6-DBI (vitamin B12 lower-ligand fragment)	582-60-5	D109360	5,6-Dimethylbenzimidazole (5,6-DBI)	≥99%	Representative lower-ligand fragment in vitamin B12 (cobalamin) systems: used as a reference in biochemistry/enzymology and vitamin-related studies; also a commonly used fragment in benzimidazole building-block and coordination-chemistry research.
Benzimidazole derivative | Extended conjugated aryl (optoelectronics / ligand)	716-79-0	P101541	2-Phenylbenzimidazole	≥98%	A more conjugated arylated benzimidazole building block: often used in emissive/optoelectronic materials (e.g., fluorescent cores, electron-transport related structures) and in coordination systems; suitable as a “conjugation–rigidity” comparison fragment.
Benzimidazole derivative | Nitro substitution (electronic effects / mechanistic control)	94-52-0	N105969	6-Nitrobenzimidazole	≥98%	Strong electron-withdrawing nitro group for tuning electronics and acid–base behavior: commonly used as a mechanistic/electronic-effect control building block to compare “substituent → electronic/H-bonding/coordination” changes in medicinal and materials chemistry.
Benzimidazole derivative | 2-amino (building block / coordination / salt form)	934-32-7	A104845	2-Aminobenzimidazole	≥97%	The 2-amino group provides a further derivatization handle (acylation/sulfonylation/coupling, etc.), commonly used in medicinal building blocks and ligand design; can also form salts to tune solubility for structure–property comparisons.
Benzimidazole derivative | 2-halo (functionalization handle)	4857-06-1	C137611	2-Chlorobenzimidazole	≥97%	A high-frequency “reaction handle” at C-2: facilitates subsequent substitution/coupling to build benzimidazole derivative libraries; suitable for route development and rapid building-block expansion.
Benzimidazole derivative | 6-halo (regioselectivity control)	4887-88-1	B137245	6-Bromo-1H-benzimidazole	≥97%	Halogen on the aromatic ring enables further cross-coupling/substitution, providing a regioselective expansion entry; commonly used to build multi-substituted benzimidazole series for SAR/material comparisons.
Sulfur-containing benzimidazole | Metal corrosion inhibition / coordination & stabilizer	583-39-1	M111104	2-Mercaptobenzimidazole	≥98%	Benzimidazole + thiol site enhances metal binding: used for corrosion inhibition of copper and alloys, suppressing metal-ion side reactions in rubber/polymer systems, and stabilization exploration; also a typical N/S coordination scaffold.
Basic monomer | 2-Methylimidazole (ZIF/MOF ligand & base)	693-98-1	M104839	2-Methylimidazole	≥98%	High-frequency “2-MeIm” ligand: one of the most commonly used ligands in ZIF-type MOF synthesis (e.g., ZIF-8); also a general organic base/nucleophilic catalyst and curing accelerator, bridging materials and organic synthesis applications.
Substituted imidazole | 4-substitution (organic base / intermediate)	822-36-6	M112296	4-Methylimidazole	≥98%	A basic substituted imidazole feedstock: used for synthetic intermediates, coordination/salt construction, and basicity control; suitable for structural comparisons of how substitution position (2- vs 4-) impacts basicity and reactivity.
Substituted imidazole | C-2 alkyl (organic base / curing accelerator / ligand)	1072-62-4	E137989	2-Ethylimidazole	≥98%	Representative substituted imidazole base: commonly used as an accelerator in epoxy curing and latent-curing system studies; also used in nucleophilic catalysis and as a coordination/ionic-liquid precursor; C-2 substitution tunes basicity, volatility, and reactivity.
Substituted imidazole | C-2 alkyl (organic base / coordination & structural control)	36947-68-9	I136584	2-Isopropylimidazole	≥98%	Branched alkyl substitution at C-2: used to compare steric/hydrophobic effects on basicity, nucleophilicity, and catalytic/curing acceleration performance; also used as a ligand and as a precursor to ionic liquids or salts.
Substituted imidazole | Alkyl substitution (curing acceleration / basicity tuning)	931-36-2	E104846	2-Ethyl-4-methylimidazole	≥96%	Substituted imidazole base: commonly used in epoxy curing acceleration and polymerization systems to tune reaction rate and exotherm window; also useful as a structural control (multi-site substitution effects on basicity/sterics).
Substituted imidazole | C-2 aryl (high-melting ligand / emissive & materials building block)	670-96-2	P124054	2-Phenylimidazole	≥98%	Aryl substitution at C-2 increases conjugation and rigidity: often used in materials chemistry (e.g., coordination luminescence systems, H-bond crystal engineering) and ligand design; also serves as a building block intermediate in organic synthesis.
Functional monomer | Imidazole-containing carboxylic acid (polymer / coordination / buffering)	104-98-3	I165655	4-Imidazoleacrylic acid	≥98%	A carboxylic acid monomer with an imidazole side group: used in functional polymers (pH responsiveness, metal-ion binding, ionic conduction) and coordination crosslinking systems; the imidazole site provides protonation/coordination functions for materials modification and interfacial chemistry.
Sulfur-containing imidazole | Metal corrosion inhibition / coordination & thio-ligand	872-35-5	M134875	2-Mercaptoimidazole	≥98%	Contains dual N/S sites: strong adsorption/coordination toward metals such as Cu/Ag; commonly used for corrosion inhibition, anti-tarnish, and surface-treatment additives; also used as a thio-ligand fragment in coordination chemistry and functional materials research.
Functional additive | Metal corrosion inhibition / copper protection (thiol imidazole)	60-56-0	M106466	2-Mercapto-1-methylimidazole	Moligand™, ≥98%	Strong adsorption/coordination on metal surfaces via S/N sites: commonly used as a corrosion inhibitor, anti-tarnish agent, or surface-treatment additive for copper/silver systems; also serves as a sulfur-containing imidazole building block in coordination/materials chemistry.
Synthetic reagent | Carbonyl activation / coupling (CDI)	530-62-1	C109315	N,N′-Carbonyldiimidazole (CDI)	≥99%	Classic activator: converts carboxylic acids into acyl imidazole intermediates for forming amide/ester/carbonate bonds; controllable byproducts and convenient handling, often selected for “mild coupling” from small scale to scale-up routes.
Synthetic reagent | Sulfonylation activation / sulfonamide synthesis	7189-69-7	S120344	1,1′-Sulfonyldiimidazole	≥98%	Sulfonylation activator: converts sulfonic/sulfonyl substrates into more reactive intermediates to facilitate sulfonamide/sulfonate ester synthesis; widely used in making sulfonyl-functional drug and materials monomers.
Synthetic reagent | Dicarbonyl activation / coupling (oxalyl diimidazole)	18637-83-7	O159886	1,1′-Oxalyldiimidazole	≥95%	Dicarbonyl activation/transfer reagent: used for carboxylic acid derivatization, coupling, and building reactive intermediates; shares the “imidazole activation” concept with CDI but with a different reactivity window, enabling comparisons of activation strength and side-reaction windows.
Synthetic reagent | Sulfonyl azidation (to sulfonyl azide / azide source)	952234-36-5	H305026	1H-Imidazole-1-sulfonyl azide hydrochloride	≥95%	A typical diazotransfer reagent: used to convert primary amines into the corresponding organic azides; assess and handle under organic azide/hazardous chemical safety norms—avoid treating it as a “mild universal azide source.”

Table E | Platform Systems | N-Alkylimidazole Precursors + Ionic Liquids (Imidazolium Salts) + NHC Precursors

Category	CAS No.	Aladdin Cat. No.	Name	Specification / Purity	Product features & applications
N-alkylimidazole | Catalytic base / ligand precursor / curing accelerator	616-47-7	M109227	1-Methylimidazole	≥99%	Common organic base and N-donor ligand: used in nucleophilic catalysis (e.g., acylation/condensation), epoxy curing acceleration, and as a precursor for coordination/ionic-liquid synthesis; a basic small-molecule tool for tuning “basicity/nucleophilicity.”
N-alkylimidazole | Organic base / ligand (substitution-effect control)	1739-84-0	D106351	1,2-Dimethylimidazole	≥98%	Substituted imidazole base: used in nucleophilic catalysis and coordination systems; suitable for structural controls linking “increased substitution/sterics → changes in basicity and reactivity,” and also used as a precursor for ionic liquids/salts.
N-alkylimidazole | Ionic-liquid precursor / catalysis & coordination	7098-07-9	E139207	1-Ethylimidazole	≥98% (GC)	Representative N-alkylimidazole: used as a precursor to ionic liquids and coordination systems, and also as a base/ligand in organic and materials reactions; often used to probe “ethyl substitution → changes in solubility and reactivity.”
N-alkylimidazole | Ionic-liquid precursor / solvent & coordination tool	4316-42-1	B152373	1-Butylimidazole	≥98% (GC)	N-alkylimidazole: commonly used to synthesize imidazolium ionic liquids, and also as an organic base/ligand and a solvation-control tool; suitable for comparing “alkyl chain length → hydrophobicity/viscosity/phase behavior.”
Ionic liquid | Imidazolium salt (EMIM⁺/Cl⁻)	65039-09-0	E120488	1-Ethyl-3-methylimidazolium chloride	≥98%	Chloride-form imidazolium ionic liquid: often used as a precursor for ionic-liquid synthesis (anion exchange to BF₄⁻/PF₆⁻/TFSI⁻, etc.); also used to dissolve/stabilize strongly polar or ionic systems (a “solvation platform” role similar to BMIMCl).
Ionic liquid | Imidazolium salt (EMIM⁺/BF₄⁻)	143314-16-3	E120493	1-Ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄)	≥98%	Representative imidazolium ionic liquid: commonly used in electrochemical electrolytes, catalytic media, and extraction/separation systems; suitable for “anion switching → viscosity/polarity/phase behavior/electrochemical window” comparisons vs TFSI⁻/PF₆⁻/Cl⁻ systems.
Ionic liquid | Imidazolium salt (TFSI⁻, electrochemistry / solvent platform)	174899-82-2	E359386	1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide	≥99%	Representative imidazolium ionic liquid: low volatility with a relatively wide electrochemical window; commonly used in electrolytes/electrochemical systems, catalysis, and separation media; also explored as a “solvent platform” to dissolve/stabilize certain poorly soluble systems.
Ionic liquid | Imidazolium salt (BMIM⁺/Cl⁻, solvation platform)	79917-90-1	B359327	1-Butyl-3-methylimidazolium chloride (BMIMCl)	≥98%	Representative chloride ionic liquid: commonly used for dissolution/processing studies of cellulose/polysaccharides, ionic-interaction models, and catalytic media; also widely used as a starting material for anion exchange to prepare other BMIM⁺ ionic liquids.
Ionic liquid | Imidazolium salt (BMIM⁺/BF₄⁻)	174501-65-6	B359377	1-Butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄)	≥98%	Representative imidazolium ionic liquid: used in electrochemistry, catalysis, and extraction/separation research; suitable for comparing how anions (BF₄⁻ vs TFSI⁻ vs Cl⁻) affect viscosity, polarity, and phase behavior.
Ionic liquid | Imidazolium salt (BMIM⁺/TFSI⁻)	174899-83-3	B101513	1-Butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIMTFSI)	≥98%	Common ionic liquid: relatively wide electrochemical window and good ionic conductivity; widely used as an electrolyte solvent, catalytic medium, and separation medium; suitable for solvent/additive screening in electrochemical/battery systems.
Ionic liquid | Imidazolium salt (BMIM⁺/PF₆⁻)	174501-64-5	B107646	1-Butyl-3-methylimidazolium hexafluorophosphate	≥97%	Common PF₆⁻-type ionic liquid: used in electrochemistry, extraction/separation, and catalytic media; comparing with BF₄⁻/TFSI⁻/Cl⁻ helps evaluate differences in hydrophobicity, viscosity, and phase separation behavior.
NHC precursor | Bulky aryl imidazolium salt (ligand precursor)	141556-45-8	B359251	1,3-Bis(2,4,6-trimethylphenyl)imidazolium chloride	≥97%	Representative “bulky aryl imidazolium” scaffold: commonly used as an NHC (N-heterocyclic carbene) ligand precursor for metal complexes/catalytic system construction; Mes substitution provides steric and electronic tuning, suitable for comparing catalytic activity and stability.
NHC precursor | IPr-type imidazolium salt (ligand precursor)	258278-25-0	B138573	1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride	≥97%	Representative IPr scaffold imidazolium salt: a high-frequency NHC precursor for preparing metal–NHC catalysts (commonly seen in cross-coupling, olefin metathesis/hydrogenation, etc.); used for ligand-series comparisons with stronger steric/electronic effects.

Note: The above are representative Aladdin products. For additional specifications, please refer to the full product list at the end of the document, or search the Aladdin website using “product name / CAS / catalog number.”

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