Solid-State Structural Study of the Charge-Transfer Complexes of 5,7,9-Trimethyl- and 2,11,20-Trithia[3_3](1,3,5)cyclophanes

摘要

5,7,9-Trimethyl[3_3](1,3,5)cyclophane (1), with two binding sites of different donating ability, adopts a C_3 conformation both in the solid state (-170 deg C) and in CD_2Cl_2 solution at -90 deg C. 5,7,9-Trimethyl[3_3](1,3,5)cyclophane-2,11,20-trione (9)has the same C_3 symmetry, while [3_3](1,3,5)cyclophane-2,11,20-trione (12) adopts the C_s structure in the solid state (-170 deg C). The structures of 1 and 9 are the first examples of C_3 or C_(3h) symmetries in the [3_3](1,3,5)cyclophanes; their preferred conformers are C_s both in solution and in the solid state. The cyclophane 1 shows much stronger donating ability than the parent [3_3](1,3,5)cyclophane (2). In the TCNQ-F_4 (1:1) complex of 1, the donor (D) and the acceptor (A) are stacked alternately, with partial and complete D-A overlaps being observed in the solid state (-170 deg C) in the forms of partial D-A overlap of the methyl-substituted benzene face and TCNQ-F_4 and of nearly complete D-A overlap of the methyl-unsubstituted benzene face and TCNQ-F_4. The former type of overlap is generally observed in the TCNQ-F_4 complexes of the [3_n]cyclophanes, and the transannular D-A distance (3.22 A) is much shorter than that in the latter (3.58 A). This supports the idea that the methyl-substituted benzene ring interacts more strongly than the methyl-unsubstituted benzene ring with the acceptor. Consistently with this, two types of acceptor columns are observed, and the transannular distances between acceptors are 3.45 A for the methyl-unsubstituted side and 3.26 A for the methyl-substituted side. In the 2,11,20-trithia[3_3](1,3,5)cyclophane (4)-TCNQ-F_4 (1:1) complex, an alternating D-A stacking similar to that in [3_3](1,3,5)cyclophane (2)-TCNQ-F_4 (1:1) is observed. The acceptors are stacked in a parallel fashion and form an infinite column, the A-A distance in the (4)-TCNQ-F_4 (1:1) complex being 3.10 A, and the acceptors in the unit cell are arranged parallel in a plane, the A-A distance being 3.12 A.