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A novel series of cyclometalated platinum(II) complexes bearing acyclic diaminocarbene (ADC) ancillary ligands were designed and prepared. Their photophysical properties were systematically studied through experimental and theoretical investigations. All complexes exhibit green phosphorescence with a quantum efficiency of up to 45% in 2 wt% doped PMMA film at room temperature. The complexes are used as light-emitting dopants for organic light-emitting diode (OLED) fabrication. The devices displayed a green emission with a maximum current efficiency of 2.9 cd A−1 and a luminance of 2700 cd m−2. These results show that these cyclometalated platinum(II) complexes can be used as efficient green emitting components of OLED devices. [ABSTRACT FROM AUTHOR]

Palladium(II) and platinum(II) complexes featuring metalla-N-heterocyclic carbenes (7–12) were synthesised via metal-mediated coupling between equimolar cis-[MCl2(CNR)2] (R = 2,6-Me2C6H3 (Xyl), 2,4,6-Me3C6H3 (Mes)) and 2-aminopyridine or 2-aminopyrazine. Thiocyanate complexes 13–18 with two thiocyanate ligands were obtained through the ligand exchange in the parent compounds 7–12 with NH4CNS in acetone/CH2Cl2. Complexes 7–18 were isolated and characterised by HRESI+-MS, IR, 1H and 13C{1H} NMR spectroscopy and single-crystal X-ray diffraction (in the case of 11, 16, and 18). The UV-vis properties of 7–18 and the electrochemical properties of 7–12 were also evaluated. To study the electronic structure and bonding nature in the new compounds, the quantum theory of atoms in molecules (QTAIM) and Mayer bond order analysis together with the extended transition state with the natural orbitals for chemical valence (ETS-NOCV) method, were used. X-ray diffraction studies and theoretical considerations indicate that the thiocyanate derivatives 16 and 18 form supramolecular dimers by two symmetrical pairs M1⋯C5 and S1⋯C2 with short intermolecular contacts between an electron-rich MII-center and thiocyanate ligand on the one side and the electron-poor π-system of an azaheterocyclic ring on the other side. Representative carbenes 8, 11 and 12 were evaluated as photocatalysts for the hydrosilylation of diphenylacetylene with triethylsilane giving 1,2-(diphenylvinyl)triethylsilane in 98% yield under visible light irradiation (blue light, 445 nm). [ABSTRACT FROM AUTHOR]

Phosphorescent PtII-based cyclometalated complexes co-crystallise with bromo- and iodosubstituted perfluorinated arenes to give 1 : 1 adducts. X-FArenes in these co-crystals act as both σh and πh donors forming co-operative C–X⋯Cl–Pt XBs and πh⋯dz2[PtII] contacts. The solid-state photophysical study revealed up to a 2-fold luminescence quantum yield increase upon co-crystallisation due to the formation of these co-operative noncovalent interactions. [ABSTRACT FROM AUTHOR]

Bis-ADC complexes cis-[Pd{C(NHC6H4NH2)N(H)R}2]Cl2 (R = Xyl 4a, Cy 4b, C6H4-4-F 4c) and cis-[Pt{C(NHC6H4NH2)N(H)R}2]Cl2 (R = Xyl 5a, Cy 5b, C6H4-4-F 5c) were synthesized via the metal-mediated coupling of two isocyanide ligands in cis-[MCl2(CNR)2] (M = Pd, Pt; R = Xyl, Cy, C6H4-4-F) and 1,2-diaminobenzene. New compounds 4c and 5a–c were characterized by HR ESI+-MS, IR, and 1H, 13C{1H} and 195Pt{1H} NMR spectroscopy; the structures of 4a and 5a were elucidated by single-crystal X-ray diffraction. The stability of the ADC complexes in aqueous media (5 mM NaCl) was monitored by UV absorption spectroscopy, HR ESI+ mass spectrometry, and 195Pt{1H} NMR spectroscopy (for 5a). Molar conductivity measurements in MeOH (ΛM = 167–173 Ω−1 mol−1 cm2) indicate that, in this solvent, the ADC complexes exist as dicationic species of [A][Q]2 type. The ADC complexes binding to CT DNA was investigated by means of spectroscopic and hydrodynamic techniques including UV absorption and circular dichroism spectroscopy, fluorescence spectroscopy, low-gradient viscometry, flow birefringence, and AFM imaging. As a result, complexes 4a and 5a were shown to bind double-stranded DNA predominantly via the formation of monofunctional adducts in the major groove of the macromolecule. Binding of the ADC complexes also provokes the formation of a large number of intermolecular DNA–DNA contacts in solution. The antiproliferative activity of all prepared ADC complexes 4a–c and 5a–c was evaluated in vitro against three human carcinoma cell lines (HT-29, MDA-MB-231, and MCF-7) and two non-tumorigenic cell lines (L929 and RC-124) and compared to that of cisplatin. Among the compounds studied, complexes 4a and 5a appeared to be the most active species with IC50 values in MCF-7 cells of about 10 μM. [ABSTRACT FROM AUTHOR]

Inspection of the X-ray structure of the newly prepared trans-[PdCl(CNXyl)ADC] (ADC = XylNH–C_;＝N–[5-iodo-2,6-dimethylpyrimidin-4-yl]) complex made it possible to identify for the first time the π-hole interaction involving the nitrogen atom of a coordinated isocyano group with a lone pair. Processing of available CSD data and results of DFT calculations revealed the possibility of two different sites for π-hole interaction involving isocyanides, i.e. both isocyano carbon and nitrogen centers are capable of acting as the π-hole donor toward lone pairs. [ABSTRACT FROM AUTHOR]

Reaction of [Ir(μ-Cl)(ppy)2]2 (1) with 4 equivs of CNC6H4X (X = F 2a, Cl 2b, Br 2c, I 2d) in the presence of 2 equivs of AgOTf in dichloromethane at 20–25 °C furnished the bisisocyanide complexes [Ir(ppy)2(CNC6H4X)2](OTf) ([3a–d](OTf); 72–87%). Reaction of [3a–d](OTf) with an excess of gaseous ammonia at room temperature gave the bisdiaminocarbene species [Ir(ppy)2{C(NH2)NHC6H4X}2](OTf) [5a–d](OTf) (73–83%); the two-step addition proceeds through an intermediate formation of appropriate monocarbene complexes [4a–d](OTf). Further reaction of [5a–d](OTf) with an excess of gaseous ammonia at 50 °C led to the cleavage of one diaminocarbene ligand to the cyanide ligand in [Ir(ppy)2(CN){C(NH2)NHC6H4X}] (6a–d) and this transformation is accompanied with the elimination of a substituted aniline. Treatment of [5a–d](OTf) with N(CH2CH2OH)3 at 50 °C resulted in the cleavage of the diaminocarbene ligand to the isocyanide and uncomplexed NH3; isocyanide remains bound to the iridium(iii) center in [Ir(ppy)2{C(NH2)NHC6H4X}(CNC6H4X)](OTf) (4a–d). All isolated compounds were characterized by elemental analyses (C, H, N), molar conductivity measurements, TG/DTA, HRESI+/−-MS, FTIR, 1D (1H, 13C{1H}, 19F{1H}) and 2D (1H,1H-COSY, 1H,13C-HMQC/1H,13C-HSQC, 1H,13C-HMBC) NMR, and also by X-ray diffraction (for the bisisocyanide 3, the diaminocarbene/isocyanide 4, the bisdiaminocarbene 5, and the diaminocarbene/cyanide 6 type complexes). [ABSTRACT FROM AUTHOR]

Reaction of [AuCl3(CNR1)] (R1 = Xyl, Cy, (S)-CHMePh) with amines unexpectedly proceeds via the redox pathway giving gold(i)–isocyanides and imines, while the addition of benzophenone hydrazone to the isocyanide ligand in [AuCl3(CNR1)] at RT leads to short-lived gold(iii) acyclic diaminocarbene complexes [AuCl3{C(NHNCPh2)NHR1}]. [ABSTRACT FROM AUTHOR]

Syntheses and characterizations of novel phosphaheterocycles, 1-phenyl-4,4-dimethyl-1,4-dihydrophosphinoline (2a) and 1-phenyl-2-bromo-4,4-dimethyl-1,4-dihydrophosphinoline (2b), and their complexes with Pd(ii) and Pt(ii) are described. Reduction of 1-phenyl-4,4-dimethyl-1,4-dihydrophosphinoline 1-oxide (1a) and 1-phenyl-2-bromo-4,4-dimethyl-1,4-dihydrophosphinoline 1-oxide (1b) using trichlorosilane in refluxing benzene gave the target phosphines in a yield of 83–87%. Reactions of phosphines with acetonitrile complexes of Pd(ii) (3) and Pt(ii) (4) yielded bis(phosphine) species [MCl2L2] (5–8). Complexes 5–8 were characterized by 1H, 13C, 31P, 195Pt NMR and HRMS. The structures of all these new complexes were determined with single crystal X-ray diffraction. The configuration of the complexes in a CDCl3 solution was investigated via comparing of 31P NMR data in solution and solid state. [ABSTRACT FROM AUTHOR]

A reaction between equimolar amounts of cis-[PdCl2(CNCy)2] (1) and indazole (HInd, 2) or 5-methylindazole (HIndMe, 3) proceeded in refluxing CHCl3 for ca. 6 h affording the aminocarbene species cis-[PdCl2{C(Ind)=N(H)Cy}(CNCy)] (4) or cis-[PdCl2{C(IndMe)=N(H)Cy}(CNCy)] (5) in good (72–83%) isolated yields. Complexes 4 and 5 were characterized by elemental analyses (C, H, N), HR ESI+-MS, IR, and 1D (1H, 13C{1H}) and 2D (1H,1H-COSY, 1H,13C-HMQC/1H,13C-HSQC, 1H,13C-HMBC) NMR spectroscopies, and complex 4 as well by X-ray diffraction. The observed coupling represents the first example of metal-mediated integration between any isocyanide and any aromatic heterocyclic system having an HN center. [ABSTRACT FROM AUTHOR]

A novel series of cyclometalated platinum(II) complexes bearing acyclic diaminocarbene (ADC) ancillary ligands were designed and prepared. Their photophysical properties were systematically studied through experimental and theoretical investigations. All complexes exhibit green phosphorescence with a quantum efficiency of up to 45% in 2 wt% doped PMMA film at room temperature. The complexes are used as light-emitting dopants for organic light-emitting diode (OLED) fabrication. The devices displayed a green emission with a maximum current efficiency of 2.9 cd A -1 and a luminance of 2700 cd m -2 . These results show that these cyclometalated platinum(II) complexes can be used as efficient green emitting components of OLED devices.

Palladium(II) and platinum(II) complexes featuring metalla-N-heterocyclic carbenes (7-12) were synthesised via metal-mediated coupling between equimolar cis -[MCl 2 (CNR) 2 ] (R = 2,6-Me 2 C 6 H 3 (Xyl), 2,4,6-Me 3 C 6 H 3 (Mes)) and 2-aminopyridine or 2-aminopyrazine. Thiocyanate complexes 13-18 with two thiocyanate ligands were obtained through the ligand exchange in the parent compounds 7-12 with NH 4 CNS in acetone/CH 2 Cl 2 . Complexes 7-18 were isolated and characterised by HRESI + -MS, IR, 1 H and 13 C{ 1 H} NMR spectroscopy and single-crystal X-ray diffraction (in the case of 11, 16, and 18). The UV-vis properties of 7-18 and the electrochemical properties of 7-12 were also evaluated. To study the electronic structure and bonding nature in the new compounds, the quantum theory of atoms in molecules (QTAIM) and Mayer bond order analysis together with the extended transition state with the natural orbitals for chemical valence (ETS-NOCV) method, were used. X-ray diffraction studies and theoretical considerations indicate that the thiocyanate derivatives 16 and 18 form supramolecular dimers by two symmetrical pairs M 1 ⋯C 5 and S 1 ⋯C 2 with short intermolecular contacts between an electron-rich M II -center and thiocyanate ligand on the one side and the electron-poor π-system of an azaheterocyclic ring on the other side. Representative carbenes 8, 11 and 12 were evaluated as photocatalysts for the hydrosilylation of diphenylacetylene with triethylsilane giving 1,2-(diphenylvinyl)triethylsilane in 98% yield under visible light irradiation (blue light, 445 nm).