A series of bis(thiocyanato)gold(I) complexes with Au-Au interactions show luminescence in the range from 500 to 670 nm. The series of salts correlates emission energy with the reciprocal of the Au-Au distance. As the Au-Au distance increases, the emission energy decreases. The ligand system provides no framework for the Au-Au interaction. The emission energy seems totally determined by the Au-Au distance.

The electronic structure of bis(thiocyanato)gold(I) complexes is studied both experimentally and theoretically. Temperature-dependent photoluminescence studies for K[Au(SCN) 2 ] reveal two unstructured luminescence bands: a strong green phosphorescence band (τ 77K ) 45.4 µs) and a weak blue fluorescence band (τ 77K ) 24.4 ns) that becomes well-resolved by cooling toward 4 K or by time-resolved measurements, representing a rare case for Au(I) compounds whereby both fluorescence and phosphorescence are observed simultaneously. Quantum mechanical calculations for dimeric models indicate Au-Au covalent bond formation in the T 1 lowest triplet excited state (2.62 Å; υ Au-Au ) 180 cm -1 ), compared to corresponding values of 2.95 Å and 84 cm -1 , respectively, for the aurophilically bound S 0 ground state. Intriguing structure-luminescence relations exist for bis(thiocyanato)gold(I) complexes with different cations such as K + , Rb + , n-Bu 4 N + , and Cs + in which the salts with shorter Au‚‚‚Au nearest-neighbor separations show blue shifts in the phosphorescence emission energies as well as smaller Stokes' shifts, contrary to the expected trends. We have also observed significantly red-shifted phosphorescence energies and larger Stokes shifts in frozen solutions of K[Au(SCN)] 2 compared to those for the crystals. The computational data suggest that the emission energy is sensitive to the counterion, in support of the experimental photoluminescence data. Full optimizations of the T 1 states for isolated dimeric models in vacuum predict a drastic rearrangement in the T 1 states in contrast to the S 0 ground state and provide a physical basis for understanding the experimental photophysical results for this class of compounds.

A library of tripodal amine ligands with two oxime donor arms and a variable coordinating or noncoordinating third arm has been synthesized, including two chiral ligands based on l-phenylalanine. Their Ni(II) complexes have been synthesized and characterized by X-ray crystallography, UV-vis absorption, circular dichroism, and FTIR spectroscopy, mass spectrometry, and room-temperature magnetic susceptibility. At least one crystal structure is reported for all but one Ni/ligand combination. All show a six-coordinate pseudo-octahedral coordination geometry around the nickel center, with the bis(oxime)amine unit coordinating in a facial mode. Three distinct structure types are observed: (1) for tetradentate ligands, six-coordinate monomers are formed, with anions and/or solvent filling out the coordination sphere; (2) for tridentate ligands, six-coordinate monomers are formed with Ni(II)(NO(3))(2), with one monodentate and one bidentate nitrate filling the remaining coordination positions; (3) for tridentate ligands, six-coordinate, bis(mu-Cl) dimers are formed with Ni(II)Cl(2), with one terminal and two bridging chlorides filling the coordination sphere. The UV-vis absorption spectra of the complexes show that the value of 10 Dq varies according to the nature of the third arm of the ligand. The trend based on the third arm follows the order alkyl/aryl < amide < carboxylate < alcohol < pyridyl < oxime.