First halogen anion-bridged (MMX)(n)-type one-dimensional coordination polymer built upon d(10)-d(10) dimers

The complex [Ag(2)(PhPPy(2))(2)(NCCH(3))(2)](ClO(4))(2) [PhPPy(2) = bis(2-pyridyl)phenylphosphine] reacts with NH(4)Cl to form an insoluble one-dimensional polymer of the type (MMX)(n), {[Ag(2)(PhPPy(2))(2)Cl](ClO(4))}(n). The binuclear unit, Ag(2)(PhPPy(2))(2)(2+), exhibits two PhPPy(2) tridentate ligands bridging the two Ag atoms in a head-to-tail fashion with C(2h) symmetry, and the Ag···Ag distance [3.0942(11) Å, 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) Å] 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 ∼520 nm.