Synthesis, structure, and spectroscopic properties of copper(II) compounds containing nitrogen–sulphur donor ligands; the crystal and molecular structure of aqua[1,7-bis(N-methylbenzimidazol-2′-yl)-2,6-dithiaheptane]copper(II) perchlorate

Abstract

The linear quadridentate N2S2 donor ligand 1,7-bis(N-methylbenzimidazol-2'-yl)-2,6-dithiaheptane (bmdhp) forms mono-and di-hydrate 1 : 1 copper(i1) complexes which are significantly more stable toward autoreduction than those of the non-methylated analogue. The deep green monohydrate of the perchlorate salt crystallises as the mononuclear aqua-complex, [Cu(bmdhp)(OH,)] [CIO4I2, in the monoclinic space group P2,/n, with Z = 4, a = 18.459(3), & = 10.362(2), c = 16.365(3) A, and B = 1 1 7.1 4(1)". The structure was solved and refined by standard Patterson, Fourier, and least-squares techniques to R = 0.047 and R' = 0.075 for 3 343 independent reflections with l > 2 4 4 . The compound consists of [Cu(bmdhp) (OH2)I2+ ions and C104counter ions. The co-ordination around copper is intermediate between trigonal bipyramidal and square pyramidal, with CU-N distances of 1.950(4) and 1.997(4) A, Cu-O(water) 2.225(4) A, and Cu-S 2.328(1) and 2.337(1) A. In the solid state, the perchlorate dihydrate's co-ordination sphere may be a topoisomer of the monohydrate's. A new angular structural parameter, 7 , is defined and proposed as an index of trigonality, as a general descriptor of five-co-ordinate centric molecules. By this criterion, the irregular co-ordination geometry of [Cu(bmdhp)(OH2)I2+ in the solid state is described as being 48% along the pathway of distortion from square pyramidal toward trigonal bipyramidal. In the electronic spectrum of the complex, assignment is made of the S(thioether) -+ Cu charge-transfer bands by comparison with those of the colourless complex Zn(bmdhp)(OH) (C104). E.s.r. and ligand-field spectra show that the copper(ii) compounds adopt a tetragonal structure in donor solvents.Continuing interest in the chemistry of copper-thioether complexes has been promoted by the occurrence of the methionine side-chain as a structurally essential active-site component in a plastocyanin and two a ~u r i n s . ~-~ The additional presence of strongly bound imidazole nitrogen has stimulated the synthesis of various types of copper compounds with biomimetic donors,6-" which are intended to probe the consequences of the nitrogenlsulphur co-ordination and irregular geometry which are the hallmarks of the protein type-1 copper centres.We have prepared a series of chelating ligands with biomimetic donor atoms of the general structure shown below.l2-l5 These quadridentate ligands contain two imidazole nitrogendonor atoms, sterically hindered because they form part of the bulky benzimidazole groups, and two thioether sulphur atoms, with a varying number of carbon atoms

Unique Ligand‐Based Oxidative DNA Cleavage by Zinc(II) Complexes of Hpyramol and Hpyrimol

“…Each pentacoordinated zinc atom is in a distorted trigonal-bipyramidal environment with a t factor of 0.79 (t = 0 for an ideal square-pyramidal geometry and t = 1 for a perfect trigonal-bipyramidal environment). [32] The equatorial plane is defined by the pyridine N12 atom and the bridging phenolate O1 atom of a pyramol ligand, and by the chloride anion Cl1 (Figure 2). …”

Catecholase Activity of a Copper(II) Complex with a Macrocyclic Ligand: Unraveling Catalytic Mechanisms

“…Each carbonate ion is thus bound in a syn, synanti fashion; for example, the oxygen atoms of the carbonate anion (O51 and O51') bridge the Cu1 and Cu1' copper atoms of two different macrocyclic rings, whereas two other oxygen atoms (O52 and O52') bind to another copper ions (Cu2 and Cu2', respectively). The coordination sphere around the Cu1 ion can be described as a weakly distorted square pyramid (t = 0.23), [26] with the atoms N12, N17, N22, and O51 occupying the basal plane and the oxygen atom O51' at a distance of 2.330(3) occupying the apical position. All copper-nitrogen distances are approximately equal (the average Cu1 À N distance is 2.03 ), whereas the O51 atom is located at a somewhat shorter distance of 1.926 (3) .…”

“…Similarly, the coordination geometry around the Cu2 ion can also be best described as a weakly distorted square pyramid (t = 0.1), [26] in which the basal plane is occupied by the nitrogen atoms N32, N37, and N42 at an average distance of 2.02 , and the oxygen atom O52 at the distance of 1.957 (3) . The axial position is occupied by the oxygen O80 atom from a coordinated water molecule at a distance of 2.267(4) .…”

Facial triad modelling using ferrous pyridinyl prolinate complexes: synthesis and catalytic applications

“…S3 and Table S7 †). On the other hand compound 15 was obtained as a five-coordinated iron complex with a square-pyramidal geometry (τ = 0.28) 27 ( Fig. 9).…”

“…27 The two independent molecules in 17 have a square pyramidal geometry (τ = 0.28/ 0.24) 27 with the basal plane formed by the tridentate ligand and one chlorine. The iron centre is 0.82/0.81 Å above this plane.…”