Diverse Structural Ag(I) Supramolecular Complexes Constructed from Multidentate Dicyanoisophorone-Based Ligands: Structures and Enhanced Luminescence

Two
multidentate ligands containing a delocalized π-electron system,
2-{5,5-dimethyl-3-[2-(pyridin-3-yl)-ethenyl]­cyclohex-2-enylidene}­propanedinitrile
(L1) and 2-{5,5-dimethyl-3-[2-(pyridin-2-yl)-ethenyl]­cyclohex-2-enylidene}­propanedinitrile
(L2), were synthesized. By self-assembly of the ligands
with silver­(I) salts, six supramolecular complexes, [Ag­(L1)­(TsO)­(H2O)]2 (1), {[Ag3(L1)2(H2O)]­(ClO4)3}n (2), {[Ag­(L1)­(NO3)]·0.5C6H6}n (3), {[Ag­(L2)­(NO3)]·0.5C6H6}n (4), [Ag­(L2)2]­(ClO4) (5), and [Ag­(L2)2]­(PF6) (6), with different structures and topologies were
obtained. In polymer 2, L1 acts as a tridentate
ligand to bind Ag­(I) ions to form a one-dimensional (1D) supramolecular
structure. However, when the ligands adopt bidentate coordination
modes to coordinate with Ag­(I) ions through the pyridyl nitrogen atom
and one cyano nitrogen atom, the dinuclear supramolecular complex 1, 1D coordination polymer 3, and two-dimensional
(2D) coordination polymer 4 were obtained. In 5 or 6, only the pyridyl nitrogen atom of L2 ligand coordinates with the Ag­(I) ion to form a mononuclear complex.
The multiple coordination modes of the multidentate ligands and the
effect of anions and solvents play important roles in the structural
and topological diversity. The luminescent properties were investigated.
Compared with the ligands, the complexes show superior luminescent
properties with red-shifted and enhanced emission as well as longer
fluorescence lifetimes, which indicates that they may be good candidates
for optical materials.