Crystal Structures and
Spectroscopic Properties of
Metal–Organic Frameworks Based on Rigid Ligands with Flexible
Functional Groups
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Abstract
Two
rigid linear ligands with alkoxy functional groups (L1 = 4,4′-(2,5-dimethoxy-1,4-phenylene)
dipyridine; L2 = 4,4′-(2,5-diethoxy-1,4-phenylene) dipyridine)
incorporating carboxyl-containing auxiliary ligands (isophthalic acid
= H<sub>2</sub>IPA; terephthalic acid = H<sub>2</sub>TPA; biphenyl-4,4′-dicarboxylate
= H<sub>2</sub>BPDC) have been adopted to build a series of complexes
with M(II) (M = Zn, Co, Cd) under solvothermal conditions. The formula
of these complexes are {[Zn(L1)(IPA)]}<sub><i>n</i></sub> (<b>1</b>), {[Zn(L1)(TPA)]·DMF}<sub><i>n</i></sub> (<b>2</b>), {[Co(L1)(TPA)(H<sub>2</sub>O)<sub>2</sub>]·2DMF}<sub><i>n</i></sub> (<b>3</b>), {[Cd(L1)(TPA)(H<sub>2</sub>O)<sub>2</sub>]·2DMF}<sub><i>n</i></sub> (<b>4</b>), and {[Co(L2)(BPDC)]·0.5H<sub>2</sub>O}<sub><i>n</i></sub> (<b>5</b>). Five complexes have been characterized
by elemental analysis, infrared spectroscopy, powder X-ray diffraction
and thermogravimetry measurements. Topological analyses reveal that
complex <b>2</b> is a 6-connected <b>pcu</b> net with
point symbol {4<sup>12</sup>·6<sup>3</sup>}, while complex <b>5</b> is a 6-connected <b>rob</b> net with point symbol
{4<sup>8</sup>·6<sup>8</sup>·8}, the other complexes <b>1</b>, <b>3</b>, and <b>4</b> can be simplified as
4-connected <b>sql</b> nets with point symbol {4<sup>4</sup>.6<sup>2</sup>}. Complexes <b>1</b>, <b>3</b>, and <b>4</b> are 2D layer motifs, <b>2</b> and <b>5</b> are
both 2-fold interpenetrating 3D frameworks. The optical absorption
spectra of <b>3</b> and <b>5</b> indicate the nature of
semiconductivity. The strong fluorescence emissions and long emission
lifetimes of <b>1</b>, <b>2</b>, and <b>4</b> display
that they are promising phosphorescent materials
