Excited state properties of the low-valent bi- and trinuclear complexes of palladium and platinum

Visible Light Responsive Dinuclear Zinc Complex Consisting of Proximally Arranged Two d10 -Zinc Centers

So far, Zn(II)-based d10 complexes have been known to be colorless unless they are accompanied by chromophoric groups, and therefore both fundamental and advanced photophysical performance of Zn centers of complexes, especially in visible-light regions has been unexplored. Here, we first demonstrate a dinuclear Zn(II) complex that shows visible light absorption using an orbital distributed over closely contacted two Zn centers experimentally determined by X-ray crystallography. A contrastive study demonstrated that intermetallic orbital interaction in dinuclear Zn(II) complex is responsible for capturing visible light to exhibit orangish yellow color, whereas an analogous one without such an interaction is colorless. This work demonstrates that introduction of Zn-Zn interactions to Zn(II) molecules contradicts the common notion that Zn is unresponsive to visible light and expands the photophysical field of zinc chemistry.

Triplet energy vs. electron transfers in porphyrin- and tetrabenzoporphyrin-carboxylates/Pd3(dppm)3(CO)2+ cluster assemblies; a question of negative charge

The simple replacement of the methyl groups by carboxylates changes the dominant quenching mechanism in dye⋯[Pd32+]_x assemblies from energy to electron transfer.

Phosphine-ligated induced formation of thallium(i) “full” Pt3TlPt3sandwich versus “open-face” TlPt3sandwich with triangular Pt3(µ2-CO)3(PR3)3units: synthesis and structural/spectroscopic analysis of triphenylphosphine [(µ3-Tl)Pt3(µ2-CO)3(PPh3)3]+and its (µ3-AuPPh3)Pt3analogue

This research constitutes an operational test to assess the influence of platinum-attached phosphine ligands in the formation process of "open-face" TlPt3 or "full" Pt3TlPt3 sandwich clusters. Accordingly, the reaction of TlPF6 with triphenylphosphine Pt4(mu2-CO)5(PPh3)4, under essentially identical boundary conditions originally used to prepare (90% yield) the triethylphosphine "full" Pt3TlPt3 sandwich, [(mu6-Tl)Pt6(mu2-CO)6(PEt3)6]+ (3) ([PF6]- salt), from Pt4(mu2-CO)5(PEt3)4 was carried out to see whether it would likewise afford the unknown triphenylphosphine Pt3TlPt3 sandwich analogue of or whether the change of phosphine ligands from sterically smaller, more basic PEt3 to PPh3 would cause the product to be the corresponding unknown triphenylphosphine "open-face" TlPt3 sandwich that would geometrically resemble the known bulky tricyclohexylphosphine [(mu3-Tl)Pt3(mu2-CO)3(PCy3)3]+ sandwich (2a). Both the structure and composition of the resulting "open-face" sandwich product, [(mu3-Tl)Pt3(mu2-CO)3(PPh3)3]+ (1a) ([PF6]- salt), were unequivocally established from a low-temperature CCD X-ray crystallographic determination. The calculated Pt/Tl atom ratio (3/1) of 75%/25% is in excellent agreement with that of 72(3)%/28(5)% obtained from energy-resolved measurements on a single crystal with a scanning electron microscope. Crystals (80% yield) of the orange-red were characterized by solid-state/solution IR and variable temperature 205Tl and 31P{1H} NMR spectra; the 31P{1H} spectra provide convincing evidence that is exhibiting dynamic behavior at room temperature in CDCl3 solution. The corresponding new "open-face" (mu3-AuPPh3)Pt3 sandwich, [(mu3-AuPPh3)Pt3(mu2-CO)3(PPh3)3]+ (1b) ([PF6]- salt), was quantitatively obtained from by reaction with AuPPh3Cl and spectroscopically characterized by IR and 31P{1H} NMR spectra. A comparative geometrical evaluation of the observed steric dispositions of the platinum-attached PR3 ligands in the "open-face" (mu3-Tl)Pt3 sandwiches of (with PPh3) and the known (with PCy3) and in the known "full" Pt3TlPt3 sandwich of (with PEt3) along with the considerably different observed steric dispositions of the PR(3) ligands in the known "open-face" (mu3-AuPCy3)Pt3 sandwich of (with PCy3) and in the known "full" Pt3AuPt3 sandwich of (with PPh(3)) has been performed. The results clearly indicate that, in contradistinction to the known triphenylphosphine Pt3AuPt3 sandwich of , PPh3 and bulkier PCy3 ligands of Pt3(mu2-CO)3(PR3)3 units are sterically too large to form "full" Pt3TlPt3 sandwiches. In other words, the nature of the thallium(I) sandwich-product in these reactions is sterically controlled by size effects of the phosphine ligands. Comparative examination of bridging carbonyl IR frequencies of and with those of closely related "open-face" and "full" sandwiches provides better insight concerning the relative electrophilic capacities of Tl+, Au+, and [AuPR3]+ components in forming sandwich adducts with Pt3(mu2-CO)3(PR3)3 nucleophiles.

Preparation, Spectroscopic Characterization, and Frontier MO Study of the Heteronuclear Luminescent [Pt(2)Au(2)(dmb)(2)(PPh(3))(4)](PF(6))(2) Cluster (dmb = 1,8-Diisocyano-p-menthane). A Cluster with a Formal Au(0)-Au(0) Bond Encapsulated inside a "Pt(2)(dmb)(2)(2+) " Fragment

The title compound is prepared from the direct reaction of Pt(2)(dba)(3) (dba = dibenzylideneacetone) and [Au(PPh(3))(2)](PF(6)) in the presence of 1,8-diisocyano-p-methane (dmb), with Pt(2)(dmb)(2)Cl(2), [Pt(4)(dmb)(4)(PPh(3))(2)](PF(6))(2), and (PPh(3))AuCl being formed as parallel products. X-ray crystallography reveals the presence of a quasi-linear PPh(3)Au-AuPPh(3) fragment encapsulated inside a "Pt(2)(dmb)(2)(2+)" ring which is axially coordinated with two PPh(3) ligands. The d(AuAu) is 2.5977(6) Å and is indicative of a strong Au-Au single bond. The IR nu(CN) data reveal that the Pt oxidation state is I, which places the Au oxidation state at 0. The PtAu distances are 2.8422(5) and 2.8082(5) Å. The Raman-active nu(Au(2)), nu(PtAu) (b(2g) + a(g)), nu(PtP), nu(AuP), and nu(PtC) are found at 121.2, approximately 100, 85.5, 162.1, 183.1, and 457.2, and 440.9 cm(-)(1), respectively. The PtAu (0.67 mdyn Å(-)(1)) and Au(2) (1.21 mdyn Å(-)(1)) force constants (F) confirm the presence of medium PtAu and strong Au(2) bonding interactions. The absorption spectra are characterized by strong bands at lambda(max) (epsilon, M(-1) cm(-1)) at 316 (32 300), 366 (37 800), and 418 nm (21 500) and lower intensity features at 516 (2860) and 655 nm (834). The cluster is luminescent at low temperatures (solid and frozen glasses), and in the solid state at room temperature, and exhibits an emission band at approximately 875 nm, and an emission lifetime, tau(e), of 4.4 +/- 0.4 ns (solvent = butyronitrile, T = 77 K).