Gold(III) complexes of asymmetrically aryl-substituted 1,2-dithiolene ligands featuring potential-controlled spectroscopic properties: an insight into the electronic properties of bis(pyren-1-yl-ethylene-1,2-dithiolato)gold(III).

The electrochemical, UV/Vis-NIR absorption, and emission-spectroscopic features of (TBA(+))(1(-)) and the corresponding neutral complex 1 were investigated (TBA(+)=tetrabutylammonium; 1(-)=[Au(III)(Pyr,H-edt)(2)](-); Pyr,H-edt(2-)=pyren-1-yl-ethylene-1,2-dithiolato). The intense electrochromic NIR absorption (λ(max)=1432 nm; ε=13000 M(-1) cm(-1) in CH(2)Cl(2)) and the potential-controlled visible emission in the range 400-500 nm, the energy of which depends on the charge of the complex, were interpreted on the grounds of time-dependent DFT calculations carried out on the cis and trans isomers of 1, 1(-), and 1(2-). In addition, to evaluate the nonlinear optical properties of 1(x-) (x=0, 1), first static hyperpolarizability values β(tot) were calculated (β(tot)=78×10(-30) and 212×10(-30) esu for the cis isomer of 1(-) and 1, respectively) and compared to those of differently substituted [Au(Ar,H-edt)(2)](x-) gold dithiolenes [Ar=naphth-2-yl (2), phenyl (3); x=0, 1].