Electronic properties and crystal structure of (2,2′-bipyridyl)-catena-µ-(oxalato-O¹O²: O^1′O^2′)-copper(II) dihydrate and aqua(2,2′-bipyridyl)-(oxalato-O¹O²)copper(II) dihydrate

Abstract

The crystal structure of the title compounds [Cu(bipy)(C204)]-2H20 (1) and [Cu(bipy)(C204) (OH2)].2H20 (2) have been determined by X-ray analysis. Compound (1) crystallises in the triclinic space group P i with a = 9.673(3), b = 8.940(3), c = 9.103(3) A, a = 105.718(3), p = 110.347(3), y = 97.539(3)', and2 = 2. The six-co-ordinate C U N ~O ~O ' ~ chromophore of (1 ) involvesan elongated rhombic octahedralstereochemistryinvolving a symmetrically co-ordinated bipy ligand (mean CU-N 2.007 A) and unsymmetrically co-ordinated bridging oxalate groups (mean Cu-0 1.988 and 2.320 A). Compound (2) crystallises in the triclinic space group Pi with a = 10.565(3), b = 7.246(3), c = 10.806(3) A, a = 102.467(3), p = 62.119(3), y = 98.134(3)", and 2 = 2. TheCuN2020' chromophore of (2) is basically square pyramidal with a symmetrically co-ordinated bipy ligand (mean CU-N 1.989 A), and a symmetrically co-ordinated oxalate group (mean Cu-0 1.953 A) in the plane of the square pyramid, and a water molecule at 2.341 A out of the plane. The electronic reflectance spectrum of (1) involves a main band at 14 500 cm-' with a resolved broad band at 9 300 cm-l, while that of (2) involves a single broad band at 15 600 cm-I, a difference that is consistent with the structures and suggests an ' electronic criterion of stereochemistry ' to distinguish these two structures.

Structure of copper- and oxalate-substituted human lactoferrin at 2.0 Å resolution

“…The 1,2-bidentate coordination of the oxalate ion is also consistent with the coordination seen in small molecule copper-oxalato species such as the [Cu-(C204)2(H20)2] 2-ion (Gleizes, Maury & Galy, 1980) and [Cu(bipy)(C204)(OH2)].2H20 and [Cu(bipy)-(C204)].2H20 (Fitzgerald et al, 1982). In the first two complexes, the oxalate is symmetrically coordinated to the copper (Cu--O bond lengths between 1.93 and 1.97,~), while the latter complex has the oxalate ion bridging between two Cu atoms, with asymmetric bidentate 1,2-coordination (the Cu--O bond lengths are 1.99 and 2.32 ,~).…”

One‐Dimensional Oxalato‐Bridged Metal(II) Complexes with 4‐Amino‐1,2,4‐triazole as Apical Ligand

“…The strongest antiferromagnetic coupling (values of J ranging from -260 to -400 cm -1 ) [12,20,21] result when the oxalato bridge is symmetrically coordinated with two short bonds to each copper() center in such a way that it is coplanar with the singly occupied molecular orbitals (SOMOs) of the copper atoms. But when one copper-bridge distance is long (i. e., oxalato bridge is asymmetrically coordinated), the two metal-centered magnetic orbitals are parallel to each other and perpendicular to the bridging ligand (Scheme 1), the interaction between the d magnetic orbitals through the oxalato ligand is poor, and a weak anti-or ferromagnetic (when the overlap is zero, accidental orthogonality) [9][10][11]14,20,[22][23][24][25] coupling results, as occurs in 1.…”

“…The difference of the Cu-O bond lengths (0.31 Å) involving the bis(bidentate) oxalato ligand is similar to those observed in other six-coordinate copper() complexes based on asymmetrically coordinated oxalato bridges. [14][15][16] The atoms involved in the four short bonds (O1, O1a, N11, N11a) define the equatorial plane of the MO 4 N 2 chromophore that forms a dihedral angle of 83.5°with the oxalato bridging ligand. .…”

Neutral and cationic mononuclear copper(II) complexes with enrofloxacin: Structure and biological activity

“…Mononuclear carboxylato copper complexes in the presence of nitrogen donor ligands have been isolated either in neutral or in cationic form [7][8][9][10][11][12][13][14][15][16][17]. The antifungal and antibacterial properties of a range of copper(II) complexes have been evaluated against several pathogenic fungi and bacteria [18][19][20][21][22][23].…”