An Infrared Study of the Metal Chelates of Some Imidazole Derivatives¹

Abstract

Infrared absorption curves have been obtained in the 2-15 µ region for a series of metal chelates of 2-(2-pyridyl)-and 2-(o-hydroxyphenyl) -derivatives of benzimidazole, imidazoline, benzoxazole and benzothiazole. Use was made of the potassium bromide pressed pellet technique for the preparation of samples. Particular attention has been focussed on the 3 µ region in order to observe the effects of coordination on the N-H stretching frequency. Coordination of the reagent with a metal ion decreases the N-H stretching frequency. This is explained in terms of resonance structures.Evidence is given for an intramolecular chelate structure in 2-( o-hydroxyphenyl) -benzimidazole. 2-(o-Hydroxyphenyl) -benzoxazole and its chelates have an absorption band at 8.0 µ (1250 kayser) which undergoes a regular shift, paralleling the usual stability order of the metals. The copper(II) chelate is at the highest frequency.

1-(4-Fluorobenzyl)-2-(pyridin-2-yl)-1H-benzimidazole

“…For the use of 2-(2-pyridyl)benzimidazole in coordination chemistry, see: Boca et al (1997);De Castro et al (1991); Khalil et al (2001); Maekawa et al (1994). For deprotonation of the NH group in 2-(2-pyridyl)benzimidazole, see: Chiswell et al (1964); Harkins et al (1956); Haga (1983). For functionalization of 2-(2-pyridyl)benzimidazole, see: Ali et al (1998); Hossain et al (2001); Sahin et al (2010).…”

“…The N-N type ligand system, 2-(2-pyridyl)benzimidazole has a venerable history in coordination chemistry (Harkins et al, 1956;Chiswell et al, 1964;De Castro et al, 1991;Maekawa et al, 1994;Khalil et al, 2001;Boca et al, 1997).…”

Bis(1,10-phenanthroline)[2-(2-pyridyl)-1H-benzimidazol-1-yl]ruthenium(II) perchlorate–toluene–acetonitrile (2/2/1)

“…The ligand 2-(2-pyridyl)benzimidazole (PIBH) has been widely used in coordination chemistry (Harkins et al, 1956;Chiswell et al, 1964;Boca et al, 1997;Shavaleev et al, 2004). Many of the reported complexes have been of interest bacause deprotonation of the coordinated imidazoles can induce switching of the luminescence and redox properties (Haga, 1983;Haga et al, 1991;Walter & Freiser, 1954).…”

Photophysical properties and computational investigations of tricarbonylrhenium(I)[2-(4-methylpyridin-2-yl)benzo[d]-X-azole]L and tricarbonylrhenium(I)[2-(benzo[d]-X-azol-2-yl)-4-methylquinoline]L derivatives (X=N–CH3, O, or S; L=Cl−, pyridine)

“…The bidentate diimine ligand 2-(pyridin-2-yl)benzo-Xazole (X = N-R, O, S) has a long history in coordination chemistry [20,21]. More recently, studies of Ru(bpy) 2 [15] and Re(CO) 3 L (L = Cl À , Br À , CF 3 SO À 3 , CH 3 CN) complexes with these ligands have focused on their structural, photoelectric, photophysical and redox properties with applications in photoelectric devices and supramolecular photochemistry in mind [22][23][24][25][26].…”