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Two types of Pt2Pb luminescent clusters were successfully prepared by the reaction of [Pt(C6F5)(bzq)(OCMe2)] (1) and [Pt(C6F5)(ppy)(dmso)] (2) with [Pb(SpyR-5)2] (R = H, CF3). Thus, whereas 5 (ppy, Spy) is generated through coordination of the pyridine-N atoms to the Pt centers, the formation of 3, 4 (bzq), and 6 (ppy, SpyCF3) is accompanied by a formal thiolate transfer from Pb(II) to Pt(II), keeping the two N atoms in the primary environment of the lead. In 5, the neutral Pb center adopts a rather stable and symmetrical "Pt2S2" coordination sphere supplemented by two Pb··Fo contacts, whereas for the remaining species several pseudopolymorphs were found depending on the solvent (3, 4) and crystallization conditions (6). This structural diversity relies on changes in the coordination mode of the SpyR ligands (μ-κS,N/μ-κ(3)S,N,S), intermetallic Pt-Pb bonds, and secondary intra- and intermolecular contacts induced by Pb-solvent binding. Notably, the changes, which entail a slight tuning of the stereochemical activity of the lone pair, have also a remarkable impact on the emissive state ((3)L'CCT/(3)L'LCT, SpyR → Pb,Pt/(C(∧)N) in nature). Clusters 3 and 4 display a distinct and fast reversible blue shift vapoluminescent response (4 shows also color changes) to donor solvents, correlated with changes in the environment of the Pb(II) ion (asymmetric hemidirected to more symmetric holodirected) upon solvent binding and, additionally, in 4 with modifications in the crystal packing, as confirmed by XRD and supported by TD-DFT calculations. 5 and 6 do not show a vapoluminescent response. However, for 6, three different and interconvertible forms, a symmetrical form (yellow 6-y) and two asymmetrical forms with a rather short Pt-Pb bond (pale orange 6·acetone and orange 6-o), exhibiting different emissions were found. Notably, slow crystallization and low concentration favor the formation of the thermodynamically more stable yellow form, whereas fast crystallization gives rise to orange solids with a remarkable red shift of the emission. Interestingly, 6 also exhibits reversible mechanochromic color and luminescence changes.

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To investigate the factors influencing the luminescent properties of cycloplatinated complexes containing aryl and SMe 2 ligands, a detailed study of the photophysical and structural properties of the complexes [Pt(p-MeC 6 H 4 )(C^N)(SMe 2 )], (C^N= benzo[h]quinolate (bzq), 1, or 2-phenylpyridinate (ppy), 2), was conducted in solution and solid state at different temperatures. Density functional theory (DFT) and Time-dependent density functional theory (TD-DFT) investigations were carried out on both the singlet (S 0 , ground) and triplet (T 1 , excited) states of these complexes for explanation of the electronic structures, absorption and emission spectra. In the solid state, these complexes display an intense phosphorescence emission which was red-shifted from 2 to 1 due to expanding of π conjugated system in cyclometalated bzq ligand. These complexes are strongly emissive in 77 K, giving emission peaks similar to those observed at ambient temperature. The complex 1 in deoxygenated CH 2 Cl 2 solution (at low concentration) gave a phosphorescence band which 2 was accompanied by a higher-energy fluorescence band (ascribed to 1 LC transition, centered on bzq ligand), and these bands were disappeared when a concentrated solution or glassy state (77 K) of the complex is in use. On the basis of theoretical calculations, the HOMO level is a mixture of platinum center and ligand orbitals, while the LUMO level is predominantly C^N ligand based. Lowest-lying excited state responsible for the phosphorescence emission (with a significantly long lifetime) is originated from mixed 3 ILCT/ 3 MLCT with some 3 L'LCT excited state and the emission is red shifted to corresponding free cyclometallating ligand.

Cyclometalated rollover complexes of the type [PtMe(κ N,C-bipyO-H)(L)] [bipyO-H=cyclometalated 2,2'-bipyridine N-oxide; L=tricyclohexylphosphine (PCy , 2 a), 2-(diphenylphosphino)pyridine (PPh py, 2 b), P(OPh) (2 c)] were synthesized by treating [PtMe(κ N,C-bipyO-H)(SMe )] (1) with various monodentate phosphine and phosphite ligands. These complexes were characterized by NMR spectroscopy, and the structure of 2 a was confirmed by single-crystal X-ray diffraction. Complex 1 was treated with bis(diphenylphosphino)methane (dppm) at a 1:1 ratio to give the corresponding [PtMe(κ N,C-bipyO-H)(κ P-dppm)] (3 b) complex, in which the dppm ligand acts as a monodentate pendant ligand. The biological activities of these complexes were evaluated against a panel of four standard cancer cell lines: lung carcinoma (A549), ovarian carcinoma (OV-90 and SKOV3), and breast carcinoma (MCF-7). Complexes 2 c and especially 3 b indicated effective potent cytotoxic activity regarding the cell lines. Electrophoresis mobility shift assays and molecular-modeling investigations were performed to determine the specific binding mode and the binding orientation of these alkylating agents to DNA. Detection of cellular reactive oxygen species was also determined.

Mononuclear complexes [Pt­(ppy)­(S∧S)] (1a, S∧S = O,O′-di­(cyclohexyl)­dithiophos­phate (ctp); 2a, S∧S = O,O′-di­(butyl)­dithiophos­phate (btp)) and [Pt­(bzq)­(S∧S)] (1b, S∧S = ctp; 2b, S∧S = btp) have been prepared by the reaction of precursor complexes [Pt­(C∧N)­Cl­(dmso)], C∧N = deprotonated form of 2-phenylpyrdine (ppy) and 7,8-benzoquinoline (bzq), and potassium salt of S∧S ligands. All complexes were characterized by NMR spectroscopy, and the structure of 2b was further identified by single crystal X-ray determination. Although the complexes are not luminescent in solution at ambient temperature, they become strong emissive materials (bright green) in solid state (at room temperature) with high quantum yields and long lifetimes in the microsecond domain. In frozen glass state or at low temperature (solid state), these complexes become better emissive in relation to room temperature. UV–vis spectra, supported by TD-DFT calculations, indicate that 1ILCT (intraligand charge transfer) predominates over the other transitions (L = C∧N cyclometalated ligand). Accordingly, 1 and 2 exhibit structured emission bands which display a large involvement of 3LCCT (ligand-centered charge transfer) with lower contribution of 3MLCT (metal to ligand charge transfer) transition in the excited states. Also, biological activities of 1 and 2 were evaluated against three human cancer cell lines including A549 (human lung cancer), SKOV3 (human ovarian cancer), and MCF-7 (human breast cancer). 2a presented an effective potent cytotoxic activity regarding to the cell lines. The cellular localization of 1a and 2a in MCF-7 human cells was investigated by fluorescence microscopy.

Cycloplatinated(ii) complexes 1–4 were synthesized and characterized. All complexes exhibit strong luminescence except 3.

Cycloplatinated(ii) complexes containing dppf ligand were prepared. These complexes exhibited high cytotoxicity and apoptosis-inducing activities to human cancer cell lines.