Crystal structures and single-crystal electron spin resonance spectra of π-π Type molecular complexes of bis(1-methyliminomethyl-2-naphtholato)copper(II)

The donor-acceptor molecular complexes of bis(1-methyliminomethyl-2-naphtholato)copper(II) [CuL₂] with 7,7,8,8-tetracyanoquinodimethane (tcnq), tetrachloro-1,4-benzoquinone (tcbq) and 1,3,5-trinitrobenzene (tnb), as well as the parent complex have been subjected to single-crystal X-ray diffraction analysis. The molecular complexes [CuL₂]·2tcnq and [CuL₂]·2tnb crystallize in the triclinic space group P1 and [CuL₂]·2tcbq crystallizes in the monoclinic space group P2₁/n, the copper atoms of all complexes being positioned at an inversion centre. The molecular complexes showed a typical π-π type structure consisting of alternately stacked π-electron donor (naphthalene moiety of copper complex) and π-electron acceptor (tcnq, tcbq and tnb) along the c axis (needle axis). The ESR spectrum for a copper(II) doped sample of diamagnetic [NiL₂]·2tnb showed simple copper quartet lines due to I = 3/2. The X-ray analyses indicated that the donor-acceptor interaction operating along the c axis gives a one-dimensional structure consisting of alternately stacked donor and acceptor molecules, but no distinct two-dimensional interaction.