9,10-Dihydroplatinaanthracenes with Aromatic Diimine Ligands: Syntheses and Spectroscopic and Computational Studies of New Luminescent Materials

9,10-Dihydroplatinaanthracenes with aromatic nitrogen ligands were synthesized, derived from 2,2′-bipyridine, 4,4′-dichloro-2,2′-bipyridine, 4,4′-dimethoxy-2,2′-bipyridine, 4,4′-bis(dimethylamino)-2,2′-bipyridine, 4,4′-di-tert-butyl-2,2′-bipyridine, 1,10-phenanthroline, 2,9-dimethyl-1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, and 2,2′-biquinoline. For comparison purposes, the N,N,N′,N′-tetramethylethylenediamine-derived compound was also obtained. A single-crystal X-ray structure determination was carried out on [H2C(C6H4)2]Pt(2,9-dimethyl-1,10-phenanthroline), revealing a pronounced boat conformation of the metallacyclic ring. The diimine-derived compounds are highly luminescent in the solid state at room temperature, as well as in frozen solution. The luminescent complexes are easily prepared by ligand substitution from the new organometallic platinum precursor {[H2C(C6H4)2]Pt(SEt2)}n (n = 2, 3). Spectroscopic data are provided on absorbance and emission in the UV–visible range. In order to obtain insight into orbital energies and the tunability of the optical properties, electrochemical data, as well as DFT and TD-DFT data, were obtained. The lowest-energy absorbances are due to charge transfer from orbitals located largely on the electron-rich metallacyclic ligand with some coefficient on Pt into π* orbitals of the diimine. Computations suggest that the low-energy bands mostly originate from charge transfer from the HOMO−2, HOMO−1, and HOMO to the LUMO (rarely LUMO+1 and LUMO+2) molecular orbitals. Emission maxima range from 536 to 690 nm.