Synthesis, Characterization, Spectroscopic and Photophysical Properties of New [Cu(NCS){(L‐N)2 or (L′‐NN)}(PPh3)] Complexes (L‐N, L′‐NN = Aromatic Nitrogen Base)

Abstract

AbstractThe syntheses, spectroscopic characterization (IR, 1H and 31P NMR, ESI‐MS) and conductivity studies of the mixed N,P‐donor complexes of copper(I) thiocyanate: [Cu(NCS)(py)2(PPh3)], (2), [Cu(NCS)(Mepy)(PPh3)]2, (3), [Cu(NCS)(phen)(PPh3)], (4), [Cu(NCS)(bpy)(PPh3)], (5), [Cu(NCS)(bpy)(PPh2py)], (6), [Cu(NCS)(py)(PPh2py)], (7), (py = pyridine; Mepy = 2‐methylpyridine; phen = 1,10‐phenanthroline, bpy = 2,2′‐bipyridyl), together with single‐crystal X‐ray structural characterizations of 2, 3, 4 (new polymorph), 5 and 6 are reported, which provides an opportunity to study the effect of the introduction of a pair of nitrogen donors, both unidentate and chelate, on the bonding parameters of the Cu/NCS/P system. Cu–P and Cu–N2(ar) are found to be similar [2.1974(5) and 2.091(2), 2.070(1) Å for py2 adduct 2, cf. 2.1748(9)–2.200(1) and 2.071(2)–2.106(4) Å for the counterpart values for bidentate adducts 4–6]. However, Cu–N(CS) and Cu–N–C are 2.013(2) Å and 157.4(2)° for py2 adduct 2 and 1.946(2)–1.981(8) Å and 166.7(2)–176.58(2)° for bidentate counterparts 4–6. The change is attributed primarily to the closure in the N–Cu–N angle [99.58(8)° for py2 2; 77.7(6)–80.5(3)° for N∧N‐bidentate donors 4–6]. In consequence of the increased steric profile of the Mepy ligand, we find the stoichiometry diminished to 1:1:1, which resulted in theformation of [(Ph3P)MepyCu(SCNNCS)Cu(Mepy)(PPh3)] dimers.TDDFT/CPCM calculations were used to clarify the type of transitions involved in the UV/Vis absorption spectra, and the corresponding experimental photoemission data wereacquired. The 31P CPMAS spectra of the copper derivatives exhibit distorted quartets that afford values for 1JCu,P. Furthermore, the quadrupole‐induced distortion factors were calculated, and in the cases of 2, 4 and 5, the quadrupole coupling constants were obtained, on the basis of the X‐ray structures.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)