Singlet ground-state geometry optimization of the monomer, four dimers,
and the trimer of [Pt(bph)(CO)
2], wherebph = biphenyl dianion, was performed at the B3LYP level of density functional theory (DFT) with a mixed basisset (6-311G** on C, O,
and H atoms; the Stuttgart/Dresden (SDD) effective core potential (ECP) on the Pt core;[6s5p3d] on the Pt valence shell). The aggregation was based on Pt-Pt binding as well as on
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and electrostaticinteractions. The lowest-lying triplet-state geometries of the monomer, one dimer,
and the trimer of the complexwere also optimized using the above theory. Significant shortening of the Pt-Pt bond was recorded in the tripletstate compared to the singlet one. A number of low-energy singlet
and triplet allowed excited states were calculatedusing time-dependent density functional theory (TDDFT)
and analyzed with respect to absorption, excitation,
andemission spectra collected under various conditions. Simulated spectra of the monomer
and dimer based on thesinglet excited states were correlated with the absorption spectrum. The emission in concentrated solution wasdue to the triplet dimer,
and the emitting states were
3MLCT
and Pt-centered states.