Synthesis And Properties Of Benzimidazole Fluorescent Compounds

Imidazoles are a kind of heterocyclic compounds containing two nitrogen atoms, and canform coordinate bonds with metal ions of enzymes in organism. For example,carbonicanhydride hydrolase, alkaline phosphamonoesterase and superoxide dismutase as akind of very important bioligand all base on the skeletons of imidazoles, and play anindispensible part on function of organism. Thereinto, benzimidazoles and their coordinationcompounds have good bioactivities such as anticancer, antiseptic, analgesic, antiphlogistic,antirheumatic, pesticidal, phytocidal and other functions. Moreover, they are a kind of veryimportant drug intermediates, and many medicines and pesticides base on the skeletons ofbenzimidazoles, so they are widely used in medicine and health care fields. In addtion,benzimidazoles are widely used sensitizers and specific materials because of their specificstructures and reactivities. 2-（2’-hydroxy phenyl） benzimidazoles can emit fluorescence of bigStokes shift and high fluorescence quantum yield through protons transfer in molecules. Inaddtion, they can form coordination compounds with transition metal resulted in the changeof their fluorescence properties. In recent decades, the synthesis and applications ofbenzimidazole derivatives have never been stopped and are underway today.This paper synthesized a series of benzimidazoles fluorescence compounds ofhydroxymethyl, chlorine methyl, carboxyl, formoxyl, nitro, methyl and other substituentsusing substituent salicylaldehyde and o-diaminobenzene as the basic raw materials.Then theirultraviolet absorption and fluorescenceemissionspectrum in ethanol were tested and theinfluence on fluorescence properties of different substituents were studied.It was founded thatFe³⁺had obvious fluorescentquenching to 4-chlorine methyl-2-{1H-benzimidazole-2}-phenolwhile other metal ions had few influences on that by testing influence on fluorescenceproperties of benzimidazoles of Cu²⁺,Zn²⁺, K⁺, Mg²⁺,Al³⁺,Ca²⁺,Cd²⁺,Co²⁺,Hg²⁺,Mn²⁺,Na+,and Fe³⁺in ethanol. It was suggested that 4-chlorine methyl-2-{1H-benzimidazole-2}-phenolhad good selectivity to Fe³⁺, so it could be further studied as Fe³⁺fluorescence chemicalsensor of fluorescentquenching.Although 2-（2’-hydroxy phenyl） benzimidazoles had many advantages such as bigStokes shift，high fluorescence quantum yield and easily coordination with transition metal,applications in the field of production and life were largely limited becaused of their baddissolubility in water. Our lab once attmpted to introduce hydroxyl, carboxyl, sulfo group andother hydrophilic groups to improve their water-solubilities, but the effect was not good. Sothis paper brought in the structure of quaternary ammonium salt in order to largely improvewater-solubilities of this kind of compounds. This paper synthesized a series of water-solublebenzimidazoles fluorescence compounds, and tested their solublity, ultraviolet absorption andfluorescenceemissionspectrum in water, and influences on their fluorescence properties of Cu²⁺,Zn²⁺, K⁺, Mg²⁺, Al²⁺, Ca²⁺,Cd²⁺,Co²⁺, Hg²⁺, Mn²⁺, Na⁺, Fe³⁺.It is discovered thatVIhad good selectivity to Cu²⁺,only Cu2+had good fluorescentquenching effect. Futhermore,spectral properties of coordination compounds formed with VI and Cu2+reacting withglutathione cysteine methyl ester hydrochloride, mercaptoacetic acid and mercaptoethylaminehydrochloride were tested. It is discovered that VI could be used as recovered sulfydrylfluorescence chemical sensor, and had good selectivity to glutathione.