Influence of Solvent and Weak C−H···O Contacts in the Self-Assembled [Pt₂M₄{C⋮C(3-OMe)C₆H₄}₈] (M = Cu, Ag) Clusters and Their Role in the Luminescence Behavior

Abstract

New alkynyl complexes [Pt2M4{CC(3-OMe)C6H4}8] (M = Ag 1, Cu 2) have been synthesized and their structures and properties compared to those of related [Pt2M4(CCPh)8] compounds. For the Pt-Ag derivatives, the X-ray structures of the discrete yellow solvate monomer, [Pt2Ag4{CC(3-OMe)C6H4}8].2THF ([1.2THF]), and the dark garnet unsolvated polymeric form, [Pt2Ag4{CC(3-OMe)C6H4}8](infinity) ([1](infinity)), are presented. The yellow form ([1.2THF]) exhibits a distorted octahedral geometry of the metal centers with the platinum atoms mutually trans and the four silver atoms in the equatorial plane. Pairs of Ag atoms are weakly bridged by THF molecules [mu-Ag2...O(THF)]. The garnet form ([1](infinity)) has an unprecedented infinite stacked chain of octahedral clusters linked by short Pt...Pt bonds (3.1458(8) A). In both forms, different types of weak C-H...O (OMe) hydrogen bonds are observed. For comparative purposes, we have also provided the crystal structures of the yellow monomer form, [Pt2Ag4-(CCPh)8].CHCl3, and the red dimer form, [Pt2Ag4(CCPh)8]2 (Pt-Pt 3.221(2) A). These clusters display intense photoluminescence in both solution and the solid state, at room temperature and 77 K. The emission observed for the yellow form [1.2THF] in the solid state is assigned to a 3MLM'CT [Pt(d)/pi(CCR) --> Pt(p(z))/Ag(sp)/pi(CCR)] state modified by Pt...Ag, Ag...Ag, and Ag...(THF) contacts. However, in the garnet form [1](infinity) and in 2, the emissions are related to the axial Pt-Pt bonds and are assigned as phosphorescence from a metal-metal-to-ligand charge-transfer (3MMLCT) excited state ([1](infinity)), or an admixture of a metal-metal (Pt-Pt) centered 3(dsigmap(z)sigma) and 3MMLCT excited state (2). For 1, a remarkable quenching and a shift to higher energies in the emission is observed on changing from CH2Cl2 to THF, and for both 1 and 2, the emission spectra at 77 K varies with the concentration, showing their tendency to stack even in glass.

Heteropolynuclear Pt(II)–M(I) Clusters with a C∧N∧C Biscyclometalated Ligand

“…Metallophilic interactions between closed or pseudo closed shell transition metals have attracted considerable interest because of their versatile applications in the field of metal cluster chemistry, 1-4 catalysis, 5,6 crystal engineering [7][8][9] and luminescent materials. [10][11][12] Squareplanar platinum (II) complexes are well-known to form heteropolynuclear clusters containing metal-metal interactions (d 8… d 10 , d 8… s 2 ) [M = Cu(I), [10][11][12][13][14][15] Ag(I), [10][11][12][15][16][17][18] Au(I), 10,15,19,20 Pb(II), [21][22][23][24] Cd(II), [25][26][27] Tl(I) [28][29][30][31] ] that display remarkable structural and photophysical properties. 32 The PtM dative bond is a particular type of metal-metal interaction which takes place between an electron rich platinum center and a Lewis acidic metal.…”

Luminescent Heteropolynuclear Complexes of 3,5‐Dimethylpyrazolate [Pt2Au2M2(Me2pz)8] (M=Ag, Cu) Showing the Synergistic Effect of Three Transition Elements in the Excited State

“…One of the best probes to investigate the metal-metal interactions is luminescence, because it is very sensitive to the change of the energies of ground and excited states. Much effort has been devoted to the study of the photophysical properties of heteropolynuclear complexes, [1][2][3][4][5][6][7][8][9][10][11] though these studies are limited to the complexes composed of two transition elements and ligands. It is thus very interesting to study the photophysical properties arising from the metal-metal interactions among three transition elements.…”

Role of Introduction of a Resistor in Series with the Working Electrode in Impedance Related Electrochemical Measurements

“…As expected, the transannular Pt⋅⋅⋅Pt separation is notably shorter in the eclipsed cluster (3.5838(3) Å, 3 vs. 3.9286(7) Å, 1 ), whereas the Pb⋅⋅⋅Pb distance is slightly longer (5.3583(4), 3 vs. 5.0893(7) Å, 1 ). It is worth noting that, although the Pt⋅⋅⋅Pt distances are in the upper range of those seen in linear‐chain Pt II complexes (3.01–3.75 Å),5e, 26 the Pb⋅⋅⋅Pb distances are out of the van der Waals limit (4.04 Å). The Pb centers complete their coordination through bonding to four alkynyl entities.…”