Crystal structure and charge transfer energies of complexes of the donor biphenylene with the acceptors TCNB and PMDA

摘要

Biphenylene:tetracyanobenzene (BPN:TCNB), C12H8:C10H2N4, crystallizes in a monoclinic lattice, space group P21/a, Z = 2, with a = 15.215(2) Å, b = 7.260(1) Å, c = 7.573(1) Å, β = 90.05(1)° at 296 K. The BPN donor and TCNB acceptor molecules form two symmetry-related mixed linear [001] stacks with the donor and acceptor molecular planes tilted to each other (within the individual stacks) at an angle of Φ = 7.6°. Biphenylene:pyromellitic-dianhydride (BPN:PMDA), C12H8:C10H2O6, crystallizes in two different monoclinic modifications, both space group P21/a, Z = 2, one red, and the other black. The red form (stable above ~400 K) with a = 9.280(1) Å, b = 11.869(2) Å, c = 7.293(1) Å, β = 98.68(2)° at ~120 K, exhibits mixed linear stacks (Φ = 4.1°). The lattice parameters of the black form (stable below ~400 K) are a = 13.368(1) Å, b = 5.809(1) Å, c = 10.443(1) Å, β = 102.30(1)° at ~120 K, and a = 13.450(2) Å, b = 5.917(1) Å, c = 10.464(2) Å, β = 101.82(2)° at 296 K. Its structure also can be viewed as a mixed linear stacking (Φ = 9.9°), but it displays exceptionally little intrastack molecular overlap. Instead, considerable two dimensional interactions among the donors and among the acceptors can be concluded. Single crystals of all three complexes, obtained by the plate sublimation technique, were optically characterized by their charge transfer absorption edges. These are analyzed in terms of the molecular parameters electron affinity and ionization energy. For BPN:TCNB an intrastack and an interstack CT-absorption edge can be distinguished.