Synthesis and characterization of the chromium(III) complexes of ethylene cross-bridged cyclam and cyclen ligands

Abstract

Dichloro(4,4,7,.2]tetradecane)chromium(III) chloride, Dichloro(4,4,7,.2]tetradecane) chromium(III) chloride, and Dichloro (4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2] hexadecane)chromium)(III) chloride have been prepared by the reaction of anhydrous chromium(III) chloride with the appropriate crossbridged tetraazamacrocycle. Aquation of these complexes proved difficult, but Chlorohydroxo(4,4,8,.2]hexadecane)chromium)(III) chloride was synthesized directly from chromium(II) chloride complexation followed by exposure or the reaction to air in the presence of water. The four complexes were characterized by X-ray crystal structure determination. All contain the chromium(III) ion in a distorted octahedral geometry and the macrocycle in the cis-V configuration, as dictated by the ethylene cross-bridge. Further characterization of the hydroxo complex reveals a magnetic moment of μ eff = 3.95 B.M. and electronic absorbtions in acetonitrile at λ max = 583nm (ε = 65.8 L/cm·mol), 431nm (ε = 34.8 L/cm·mol) and 369nm (ε = 17 L/cm·mol).

Crystal structures of two cross-bridged chromium(III) tetraazamacrocycles

“…The smaller, low-spin Co III ion fits into the pocket of the macrocyle better than Cr III . Chromium(III) complexes similar to (I) and (II) but crystallized with different anions have been reported before (Maples et al, 2009). The chloride analogue of (I) has bond angles of 160.83 (19) and 83.50 (18) about the chromium ion and a mean Cr-N bond length of 2.08 Å , which are in good agreement with (I), demonstrating the counter-anion has very little effect on the coordination about the metal.…”

“…Since then, their transition metal complexes have become important to the fields of oxidation catalysis (Yin et al, 2007;Dong et al, 2013), medical/biological imaging (Boswell et al, 2004;Sprague et al, 2007;Silversides et al, 2011) and chemokine receptor antagonism (Lewis et al, 2005;Valks et al, 2006;Smith et al, 2012) due to the combination of restricted macrocycle configuration and kinetic inertness inherent to these ligands.Chromium(III) complexes have played an important role in characterizing new ligands due to their relative kinetic inertness (Cotton & Wilkinson, 1988). Yet, to date, only one report of the chromium coordination chemistry of these macrobicyclic ligands has appeared in the literature (Maples et al, 2009). In order to expand the range of metal ions that can be coordinated by these remarkable ligands (Hubin, 2003), we are exploring further the structural chemistry of chromium cross-bridged tetraazamacrocyclic complexes and report synthesis and crystal structures of dichlorido(4,10-dimethyl-1,4,7,10-tetraazabicyclo[5.5.2]tetradecane)chromium (III) hexafluoridophosphate, (I), and dichlorido (4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane)chromium(III)hexafluoridophosphate, (II).…”

Investigation on Spectroscopic, Thermal and Antimicrobial Activity of Newly Synthesized Binuclear Cr(III) Metal Ion Complex

“…Thus  eff obtained is known as effective magnetic moment. The magnetic moment of this complex was determined on the solid as µ eff = 3.79 B.M., which corresponds to three unpaired electrons and indicate that the synthesized Cr(III) complex is paramagnetic and might be having octahedral geometry [16][17][18].…”

Cytotoxic, antiglycation and carbonic anhydrase inhibition studies of chromium(III)-aroylhydrazine complexes

“…Molar absorptivity values suggest these transition as Laporte forbidden, spin allowed transitions. The presence of these bands proves the octahedral geometry of complexes [59,60]. All chromium(III)-aroylhydrazine complexes showed these transitions with low molar absorptivity values (33-347 M -1 .cm -1 ) except 4 A2g (F) → 4 T1g (P) showing higher molar absorptivity value (6793-36557 M -1 .cm -1 ).…”