Luminescence studies of new [C,N,N′] cyclometallated platinum(II) and platinum(IV) compounds

The synthesis of six novel cyclometallated platinum(IV) compounds (3a–3c and 4a–4c) derived from ligand (4-FC6H4)CHN(CH2)3N(CH3)2 (L) was achieved by intermolecular oxidative addition of halogens to cyclometallated platinum(II) compounds [Pt(CH3){(CH3)2N(CH2)3NCH(4-FC6H3)}] (1) and [PtX{(CH3)2N(CH2)3NCH(4-FC6H3)}] (2a, XCl; 2b, XBr; 2c, XI). While compound 2b could be obtained from 2a through Cl for Br substitution reaction, 2c was best obtained through cyclometallation of ligand L with [PtI2(dmso)2]. The X-ray molecular structures of [C,N,N′] platinum(II) (2b) and platinum(IV) (3b and 4b) cyclometallated compounds and of the [N,N′] platinum(II) compound Ib, all of them containing bromido ligands, are reported. The absorption and emission spectra were also studied in dichloromethane solution at room temperature. All compounds, except 3c and 4c arising from oxidative addition of iodine, display a broad emission band in the 340–360 nm range, attributed to platinum disturbed intraligand (IL) transitions, when excited at the highest energy band, and higher emission intensities were observed, in general, for cyclometallated platinum(IV) compounds.