Inorganic Chemistry, Vol.49, No.23, 11069-11076, 2010
First Halogen Anion-Bridged (MMX)(n)-Type One-Dimensional Coordination Polymer Built upon d(10)-d(10) Dimers
The complex [Ag-2(PhPPy2)(2)(NCCH3)(2)](ClO4)(2) [PhPPy2 = bis(2-pyridyl)phenylphosphine] reacts with NH4Cl to form an insoluble one-dimensional polymer of the type (MMX)(n), {[Ag-2(PhPPy2)(2)Cl](ClO4)}(n). The binuclear unit, Ag-2(PhPPy2)(2)(2+), exhibits two PhPPy2 tridentate ligands bridging the two Ag atoms in a head-to-tail fashion with C-2h symmetry, and the Ag center dot center dot center dot Ag distance [3.0942(11) angstrom, X-ray] suggests argentophilic interactions. Each Ag center adopts a distorted trigonal-bipyramidal geometry, coordinated by one P atom and two pyridyl arms at the equatorial positions and interacting with one Cl ion and one Ag ion at the axial positions. The short Ag-Cl bond length [2.5791(7) angstrom] indicates the presence of some covalent character. The solid-state absorption bands spread all the way to 600 nm have been interpreted by means of density functional theory (DFT) and time-dependent DFT (B3LYP), and the lowest-energy excited states are assigned to metal/halide-to-pyridyl charge transfer, consistent with the d(10) electronic configuration of Ag. The calculated oscillator strengths are low because of the poor molecular orbital overlaps in the charge-transfer components. The novel material exhibits a luminescence band centered at about similar to 520 nm.