Abstract
The trans-Pt(PMe3)(2) (C CC6H4CN)(2) organometallic ligand L1, which is prepared from 4-ethynylbenzonitrile and cis-Pt(PMe3)(2)Cl-2, binds CuX salts to form two strongly luminescent two-dimensional coordination polymers (CPs) [{Cu-2(mu(2)-X)(2)}(2)(mu(4)-L1)](n)(X = I, CPI; X = Br, CP2). The emission quantum yields, Phi(e )approximate to 30% at 298 K, are the largest ones for all CPs built upon the trans-Pt(PMe3)(2) (C= CC6 H4X)(2) motifs (X = SMe, CN). X-ray crystallography reveals that, to accommodate these layered CPs, LI must undergo major distortions of the C C-C angles (similar to 159 degrees) and significant rotations about the Pt-CC bonds, so that the dihedral angles made by the two aromatic planes is 90 degrees in a quasi-identical manner for both CPs. Together, these two features represent the largest distortion for trans-Pt(PMe3)(2) (C CC6H4X)(2) complexes among all of the CPs built upon this type of ligand (2 of 16 entries). Concurrently, CP1 and CP2 also exhibit the most red-shifted emissions (lambda(max) = 650 and 640 nm, respectively) known for this type of chromophore at room temperature. The {Cu-2 (mu(2) -X)(2)} rhomboids adopt the trans-(X=I, common) and cis-geometries (X = Br, extremely rare) making them "isomers" if excluding the fact that the halides are different. Density functional theory (DFT) and time-dependent DFT suggest that the triplet emissive excited state is metal/halide-toligand charge transfer in both cases despite this difference in rhomboid geometry.
