Synthesis, structure, and antioxidative properties of a copper(II) complex with 1,2‐bis(benzimidazol‐2‐yl)ethane ligand

Abstract

1,2-Bis(benzimidazol-2-yl)ethane (bbe) and its copper(II) complex, {[Cu(bbe) Br 2 ] 2 }Á2DMF (1), have been synthesized and characterized by elemental analysis, ultraviolet-visible, and infrared spectra. The single crystal structure analysis of 1 shows two crystallographically independent but chemically identical [Cu(bbe)Br 2 ] molecules. The coordination geometry of the copper atoms may best be described as a distorted tetrahedron (τ 4 = 0.740 for Cu1 and 0.696 for Cu2). The cyclic voltammogram of complex 1 represents quasi-reversible Cu 2+ /Cu + pairs. in vitro antioxidant tests showed that complex 1 has significant antioxidant activity against superoxide and hydroxy radicals. Photoluminescence investigations showed that the fluorescence intensity of complex 1 is significantly weaker than that of the ligand. This may be due to the paramagnetic effect of divalent copper to cause quenching of fluorescence. K E Y W O R D S 1,2-bis(benzimidazol-2-yl)ethane, antioxidant activity, copper(II) complex, crystal structure, electrochemistry, photophysical property

CuII Pyrazolyl‐Benzimidazole Dinuclear Complexes with Remarkable Antioxidant Activity

“…Cu II coordination complexes have been widely explored for their potential antioxidant activities [7,9,12,35,38] . Still, significant improvements are of interest.…”

“…Cu II coordination complexes have been widely explored for their potential antioxidant activities. [7,9,12,35,38] Still, significant improvements are of interest. In this context, we have investigated the antioxidant property of intermediates 3 and 4 (Scheme S2), L, C 1/ C 2 , and C 3 .…”

“…In particular, Cu II complexes tethered with heterocyclic moieties have received much interest as antioxidant agents. [7,9,[33][34][35][36] Continuing research along this line, [37][38][39][40] we have designed a new benzimidazole derivative functionalized with a pyrazole unit leading to L, namely 1-n-butyl-2-((5-methyl-1H-pyrazole-3yl) methyl)-1H-benzimidazole (Scheme 1), by applying a recently conceived design approach. [37] A complexation reaction of L and Fe II chloride followed by addition of Cu(NO 3 ) 2 • 3 H 2 O led to an oxidation reaction involving the methylene group linking the benzimidazole and pyrazole moieties in L to form the ligand L' (Scheme 1).…”

Two silver(I) complexes: Synthesis, structures, and electrochemicalH2O2sensing

“…The geometry for a four‐coordinated coordination polymer can be determined to use the τ 4 geometry index, where the value of τ 4 varies from 0 (square planar) to 1 (regular tetrahedral). [ 47 ] The coordination geometry of Ag(I) ions in 2 may best be described as a distorted tetrahedron ( τ 4 = 0.65 for Ag1 and 0.84 for Ag2). The terephthalate in 2 adopted two different coordination modes: bidentate chelating (Ag1) and monodentate bridging (Ag2).…”

Two binuclear silver(I) complexes containing V‐shaped bis (benzimidazole) ligands: Syntheses, structures, and electrochemical sensing toward hydrogen peroxide

“…The geometry for a four‐coordinated complex can be determined to use the τ 4 geometry index, where the value of τ 4 varies from 0 (square planar) to 1 (regular tetrahedral). [ 56 ] The coordination geometry of Ag(I) ions in complex 1 may best be described as a distorted tetrahedron ( τ 4 = 0.78 for Ag1 and 0.79, for Ag2). Both Ag(I) centers in complex 2 are three‐coordinated which contains an oxygen atom from an isophthalate and two nitrogen atoms from a L 2 ligand.…”