A series of square planar [Pt(N^C)(NHC)L] complexes containing cyclometallated N^C ligands (phenylpyridine and benzoquinoline) and N-heterocyclic carbene (NHC) – N^C = 2-phenylpyridine, 7,8-benzoquinoline; NHC = 1,3-dibenzylbenzimidazolium, 1,3-diethylbenzimidazolium, 1,3-dibenzylimidazolium; L = Cl, Br, –C₂Ph – have been synthesized in moderate to good yields. The complexes obtained were characterized using chemical analysis, MS-ESI spectrometry, NMR spectroscopy and X-ray crystallography. The complexes display moderate to strong phosphorescence in solution (Q.Y. 0.3–7.9%) and in the solid state (Q.Y. 2.7–16.0%), which is related to metal modulated intraligand π–π* transitions located at the aromatic system of cyclometallated ligands with some contribution of the MLCT excited state. Emission lifetimes fall in the range of 0.2–1.5 μs in solution and amount up to 13 μs in the solid state. Analysis of the spectroscopic data together with the density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations clearly support this assignment and show negligible contribution of the auxiliary ligands to the emissive excited states. The compounds obtained were also used to prepare organic light emitting diode (OLED) devices, which display good luminance efficiency emitting in the green area of the visible spectrum.

The reactions of gold acetylides (AuC₂R)_n with triphosphine ligands PPh₂-(CH₂)_n-PPh-(CH₂)₂-PPh₂ (n = 1, dpmp; 2, dpep) in the presence of M⁺ ions (M = Cu, Ag) lead to an assembly of the heterometallic clusters, the composition of which is determined by the steric bulkiness of the alkynyl groups and the flexibility of the phosphine motifs. For R = Ph, an unprecedented hexanuclear complex [Au₅Cu(C₂R)₄(dpmp)₂]²⁺ (1) was isolated, while for the aliphatic alkynes (R = 1-cyclohexanolyl, 2-borneolyl, 2,6-dimethyl-4-heptanolyl) a family of compounds based on a tetrametallic framework was prepared, [Au₃Cu(C₂R)₃(dpmp)]⁺ (2, R = 1-cyclohexanolyl), [Au₃M(C₂R)₃(dpep)]₂ ⁺² (3, M = Cu, R = 1-cyclohexanolyl; 4, M = Cu, R = 2-borneolyl; 5, M = Ag, R = 2-borneolyl), and [Au₃Ag(C₂R)₃(dpep)]⁺ (6, R = 2,6-dimethyl-4-heptanolyl). Clusters 1, 2, and 4–6 were studied by X-ray crystallography. The NMR spectroscopic investigations showed that 1 and 3–5 are stereochemically non-rigid in solution and reversibly undergo possible dissociation (3) or isomerization (4, 5) processes. All the title complexes exhibit room temperature luminescence in the solid state in the spectral region from 414 to 566 nm, showing a dependence of emission energy on the structure and composition of the metal core. Computational studies with density functional methods were carried out to rationalize the dynamic and photophysical behavior of these compounds.