Inter- and Intramolecular π-Stacking Interactions incis-Bis{1-(9-anthracene)}phosphirane Complexes of Platinum(II)

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Abstract
The bis{1-(9-anthracene)phosphirane}dithiolatoplatinum(II) complexes, Pt{1-(9-anthracene)phosphirane}2(dithiolate), where dithiolate = 1,1-dimethoxycarbonyl-ethylene-2,2-dithiolate (dmdt) (2), 1,1-diethoxycarbonyl-ethylene-2,2-dithiolate (dedt) (3), 1-ethoxycarbonyl-1-cyano-ethylene-2, 2-dithiolate (ecdt) (4), and 1,1-dicyano-ethylene-2,2-dithiolate (dcdt) (5), were prepared from cis-dichlorobis{1-(9-anthracene)phosphirane}platinum(II) (1). Complexes 3 and 5 were characterized by X-ray crystallography and were found to have vastly different crystal and molecular structures. The crystal and molecular structure of 3 is dominated by intramolecular π-stacking between the anthracene rings of the cis-bis(anthracene)phosphiranes with a ring···ring separation of 3.48(6) Å. The molecular structure of 5 does not exhibit an intramolecular interaction between the anthracene rings. Instead, the crystal structure of 5 shows significant intermolecular π-stacking between the anthracene rings of the phosphirane ligands of adjacent molecules packed in the crystal lattice. The intermolecular stacking interaction results in a ring···ring separation of 3.33(4) Å. Complexes 2−5 were found to emit at 530 nm at low temperatures in the solid state. Complex 5 emits strongly in fluid THF or benzene solution at 430 nm.