Lin-Xi Shi

Effective visible-light driven CO2 photoreduction via a promising bifunctional iridium coordination polymer

A promising coordination polymer photocatalyst (Y[Ir(ppy)2(dcbpy)]2[OH]) (Ir-CP, ppy = 2-phenylpyridine, dcbpy = 2,2′-bipyridine-4,4′-dicarboxylate) based on a highly efficient light-harvesting Ir unit, Ir(ppy)2(Hdcbpy), has been obtained, with good stability and exhibiting visible-light absorption over a broad range, arising from the metal-to-ligand charge transfer (3MLCT) and ligand-to-ligand charge transfer (LLCT). The designed Ir-CP heterogeneous photocatalyst acts as both a photosensitizer to harvest visible light, and an active catalyst for CO2 photoreduction. Due to the broad absorption in the UV-visible region and long-lived excited states of Ir-CP, the photocatalyst can efficiently catalyze CO2 reduction under visible-light irradiation in a heterogeneous photocatalytic system. For the first time, the remarkable photocatalytic efficiency of Ir-CP under visible-light irradiation (38 μmol HCOO− was produced in 6 h) was shown. Moreover, Ir-CP shows high photostability during CO2 photoreduction, which promotes the recyclability of the heterogeneous photocatalyst.

Conformation control of a flexible 1,4-phenylenediacetate ligand in coordination complexes: a rigidity-modulated strategy

Five coordination complexes based on the flexible ligand 1,4-phenylenediacetic acid (H2pda), formulated as Zn(trans-pda) (1a), Mn(H2O)2(trans-pda) (1b), [M(cis-pda)(4,4′-bipy)]·H2O (M = Zn (2a), Co (2b), Cd (2c); H2pda = 1,4-phenylenediacetic acid; 4,4′-bipy = 4,4′-bipyridine), are reported. The crystal structures of the as-synthesized complexes were determined by single-crystal X-ray diffraction analyses. Complexes 1a and 1b have similar three-dimensional (3-D) network structures built by tetrahedral Zn nodes (for 1a) or octahedral Mn nodes (for 1b) and trans-pda2− bridges. Complexes 2a, 2b, and 2c possess similar two-dimensional (2-D) layered structures constructed from interconnecting metal-cis-pda2− double chains by 4,4′-bipy ligands. It is interesting that conformation of the flexible pda2− ligand is modulated in presence of the rigid 4,4′-bipy ligand. The trans-pda2− ligand was typically isolated in a single pda2− system whereas the cis-pda2− ligand was observed in a mixed pda2−/4,4′-bipy system. Furthermore, the dimensionalities of the complexes vary from 3-D (1a and 1b) to 2-D (2a, 2b, and 2c) when auxiliary 4,4′-bipy ligands were introduced. The photoluminescent studies on solid-state samples of complexes 1a, 2a and 2c indicate that the complexes exhibit intense fluorescent emissions at room temperature.

Preparation, characterization, and photophysical properties of Pt-M (M = Ru, Re) heteronuclear complexes with 1,10-phenanthrolineethynyl ligands

When 3-ethynyl-1,10-phenanthroline (HCCphen) or 3,8-diethynyl-1,10-phenanthroline (HCCphenCCH) is utilized as a bifunctional bridging ligand via stepwise molecular fabrication, a series of Pt-Ru and Pt-Re heteronuclear complexes composed of both platinum(II) terpyridyl acetylide chromophores and a Ru(phen)(bpy)2/Re(phen)(CO)3Cl subunit were prepared by complexation of one or two Pt((t)Bu3tpy)(2+) units to the mononuclear Ru(II) or Re(I) precursor through platinum acetylide sigma coordination. These Pt-Ru and Pt-Re complexes exhibit intense low-energy absorptions originating from both Pt- and Ru (Re)-based metal-to-ligand charge-transfer (MLCT) states in the near-visible region. They are strongly luminescent in both solid states and fluid solutions with a submicrosecond range of lifetimes and 0.27-6.58% of quantum yields in degassed acetonitrile. For the Pt-Ru heteronuclear complexes, effective intercomponent Pt --> Ru energy transfer takes place from the platinum(II) terpyridyl acetylide chromophores to the ruthenium(II) tris(diimine)-based emitters. In contrast, dual emission from both Pt- and Re-based (3)MLCT excited states occurs because of less efficient intercomponent Pt --> Re energy transfer in the Pt-Re heteronuclear complexes.

Diplatinum alkynyl chromophores as sensitisers for lanthanide luminescence in Pt2Ln2 and Pt2Ln4 (Ln = Eu, Nd, Yb) arrays with acetylide-functionalized bipyridine/phenanthroline

Incorporation of diplatinum complex Pt2(micro-dppm)2(bpyC[triple bond]C)4 or Pt2(mu-dppm)2(phenC[triple bond]C)4 with Ln(hfac)3(H2O)2 (Ln = Nd, Eu, Yb) gave a series of Pt2Ln2 and Pt2Ln4 bimetallic arrays, in which the excitation of d(Pt) -->pi*(R-C[triple bond]C) MLCT absorption induces sensitisation of lanthanide luminescence through efficient d --> f energy transfer from Pt(II) alkynyl chromophores.

Luminescent heterohexanuclear complexes with platinum alkynyl and silver diphosphine as components

Reactions between the building blocks [Ag2(mu-Ph2PXPPh2)2(MeCN)2]2+ and [Pt(C[triple bond]CC6H4R-p)4]2- (R = H, CH3) afforded strongly luminescent acetylide-linked neutral heterohexanuclear complexes Pt2Ag4(mu-Ph2PNPPh2)4 (C[triple bond]CC6H4R-p)4 (R = H, 1; CH3, 2) for X = NH, but a heterotrinuclear complex cation [PtAg2(mu-PPh2CH2PPh2)2 (C[triple bond]CC6H5)2(CH3CN)2]2+ (3(2+)) for X = CH2.

Using phosphorescent PtAu3 clusters for superior solution-processable organic light emitting diodes with very small efficiency roll-off

A family of highly phosphorescent PtM3 (M = Au, Ag) aromatic acetylide cluster complexes supported with tetraphosphine and stabilized by μ-chloride were synthesized by the use of weakly luminescent mononuclear Pt(PPh3)2(CCR)2 (R = aryl) as precursors. The formation of PtM3 cluster complexes involves the abstraction of chloride from dichloromethane. The dramatic difference between PtAg3 and PtAu3 cluster structures arises from the location of the Pt atom, which is at the center of the triangle-planar PtM3 cluster for M = Ag whereas at one of the three corners in the PtM3 triangle plane for M = Au. Perturbation of the chloride ion in complexation by using a halide-abstracting agent results in the formation of PtM2 heterotrinuclear structures as demonstrated by X-ray crystallography. The PtAu3 complexes display intense phosphorescence with quantum yields of over 90% in doped films. High-efficiency OLEDs based on PtAu3 complexes were attained with an external quantum efficiency (EQE) over 18%. Most importantly, the optimized devices exhibit extremely small efficiency roll-off (less than 1%) at a practical brightness over 1000 cd m−2, which is one of the best performances for solution-processable phosphorescent OLEDs.