Structure-property relationships in PtII diimine-dithiolate nonlinear optical chromophores based on aryl-ethylene-1,2-dithiolate and 2-thioxothiazoline-4,5-dithiolate.

Eighteen new [Pt II(NN)(SS)] complexes [23-40; NN = diimine: 2,2'-bipyridine, 1,10-phenanthroline and alkyl/aryl-substituted derivatives; SS = arylethylene-1,2-dithiolate (R-edt 2-: R = phenyl, 2-naphthyl, 1-pyrenyl), N-substituted 2-thioxothiazoline-4,5-dithiolate (R-dmet 2-: 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 (27-29, 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 (CH 2Cl 2, CHCl 3, CH 3CN, 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 23-40, first static hyperpolarizability values β tot were calculated both in the gas phase and in CH 2Cl 2, the highest values being obtained for [Pt(NN)(Me-dmet)] complexes (NN = 4,4'-diphenyl-2,2'-bipyridine and 4,7-diphenyl-1,10-phenanthroline; β tot = 691 × 10 -30 and 604 × 10 -30 esu, respectively). Eighteen [Pt(NN)(SS)] complexes (NN = diimine; SS = arylethylene-1,2-dithiolate, N-substituted 2-thioxothiazoline-4,5-dithiolate) have been prepared. All complexes feature a notable negative solvatochromism and potential SONLO properties on the basis of their GS electronic structures.