Six New Crystalline Clathrates of Cyclotricatechylene (CTC), Including Two Donor-Acceptor Complexes

Abstract

Abstract Dark blue [CTC]₂•tcne•6thf and dark green [CTC]₂•tcnq•4thf are both exclusion complexes, with the cyanoalkene acceptor being sandwiched between the catechol rings of two CTC host molecules. There is also extensive hydrogen bonding between the CTC and tcne or tcnq molecules, which is unusual for crystals containing these cyanoalkenes. Crystallographic, IR and UV/vis data show that these are typical donor:acceptor complexes, with strong charge-transfer interactions between the CTC and cyanoalkene acceptors. These are the first donor:acceptor complexes of a cyclotriveratrylene (CTV)-derived host, and the first crystallographically characterised adducts between tcne or tcnq and an organic cavitand. The solvate CTC•3.5thf•0.5H₂O adopts a novel nanoporous crystal lattice, composed of undulating hydrogen-bonded sheets of CTC molecules. In contrast, the clathrates CTC•2EtOH, CTC•3dma and CTC•5dmso all adopt structures that are related to previously reported clathrates of CTC, containing hydrogen bonded bilayers or bis-monolayers of CTC molecules. The CTC molecules in all six structures contain included guest solvent. This contrasts with CTV clathrate crystals, which rarely contain included solvent.