Structure-Property Relationships in PtII Diimine-Dithiolate Nonlinear Optical Chromophores Based on Arylethylene-1,2-dithiolate and 2-Thioxothiazoline-4,5-dithiolate

Eighteen new [PtII(N?N)(S?S)] complexes [2340; N?N = diimine: 2,2'-bipyridine, 1,10-phenanthroline and alkyl/aryl-substituted derivatives; S?S = arylethylene-1,2-dithiolate (R-edt2: R = phenyl, 2-naphthyl, 1-pyrenyl), N-substituted 2-thioxothiazoline-4,5-dithiolate (R-dmet2: R = methyl, ethyl, phenyl)] have been synthesized and characterized by spectroscopic (UV/Vis/NIR, fluorescence) and electrochemical (CV) measurements. Single-crystal X-ray diffraction analysis allowed structural characterization of five of the complexes (2729, 31, and 37). Structural modifications capable of affecting the nature and energies of the frontier molecular orbitals in these systems were assessed and hybrid DFT and time-dependent (TD) DFT calculations, carried out both in the gas phase and in the presence of several solvents (CH2Cl2, CHCl3, CH3CN, acetone, thf, dmf, dmso, and toluene), allowed the trends observed in the voltammetric data and in the energies of the peculiar solvatochromic visible absorption bands to be rationalized. In addition, to evaluate the second-order nonlinear optical properties of 2340, first static hyperpolarizability values beta tot were calculated both in the gas phase and in CH2Cl2, the highest values being obtained for [Pt(N?N)(Me-dmet)] complexes (N?N = 4,4'-diphenyl-2,2'-bipyridine and 4,7-diphenyl-1,10-phenanthroline; beta tot = 691 x 1030 and 604 x 1030 esu, respectively).