Iodine Release and Recovery, Influence of Polyiodide Anions on Electrical Conductivity and Nonlinear Optical Activity in an Interdigitated and Interpenetrated Bipillared-Bilayer Metal–Organic Framework

{[Cu6(pybz)8(OH)2]·I5–·I7–}n (1), obtained hydrothermally by using
iodine molecules as a versatile precursor template, consists of a
cationic framework with two types of zigzag channels, which segregate
I5– and I7– anions. The framework exhibits the first observed bipillared-bilayer
structure featuring both interdigitation and interpenetration. 1 displays high framework stability in both acidic (HCl) and
alkaline (NaOH) solutions. 1 slowly releases iodine in
dry methanol to give [Cu6(pybz)8(OH)2]­(I–)2·3.5CH3OH (1′) and partially recovers iodine from cyclohexane
to form [Cu6(pybz)8(OH)2]­(I–)2·xI2 (1″). Differences of up to 100 times in electrical conductivity
and of 4 times in nonlinear optical activity (NLO) have been measured
between 1 and 1′. This compound is
one of few displaying multifunctionality, electrical conductivity,
NLO, and crystal–crystal stability upon release and recovery
of iodine. It is also unique in the iodine release from polyiodide
anions in a metal–organic framework.