Cd(II) and Cu(II) coordination polymers based on a multidentate N-donor ligand: syntheses, crystal structures, optical band gaps, and photoluminescence

<div><p>Four Cd(II)- and Cu(II)-containing coordination polymers (CPs) based on a multidentate N-donor ligand and varied dicarboxylate anions, [Cd(3,3′-tmbpt)(<i>p</i>-bdc)]·2.5H₂O (<b>1</b>), [Cd(3,3′-tmbpt)(<i>m</i>-bdc)]·2H₂O (<b>2</b>), [Cu(3,3′-tmbpt)(<i>m</i>-bdc)]·H₂O (<b>3</b>), and [Cu(3,3′-tmbpt)(<i>p</i>-bdc)]·2H₂O (<b>4</b>), where 3,3′-tmbpt = 1 − ((1<i>H</i>-1,2,4-triazol-1-yl)methyl)-3,5-bis(3-pyridyl)-1,2,4-triazole, <i>p</i>-H₂bdc = 1,4-benzenedicarboxylic acid, and <i>m</i>-H₂bdc = 1,3-benzenedicarboxylic acid, have been prepared hydrothermally. The structures of the compounds were determined by single-crystal X-ray diffraction analyses and further characterized by infrared spectra and elemental analyses. Compound <b>1</b> exhibits a 3-D twofold interpenetrating framework with a 6⁵·8 CdSO₄ topology. Compound <b>2</b> is a 2-D layer containing meso-helical chains with a 4⁴·6² sql topology. Compound <b>3</b> shows a 1-D → 3-D interdigitated architecture while <b>4</b> displays a 2-D → 3-D interdigitated architecture. The structural differences of the compounds indicate that the dicarboxylate anions and the central metal ions play important roles in the resulting structures of CPs. Optical band gaps and solid-state photoluminescent properties have also been studied.</p></div

Synthesis, structure, and properties of a new Co(II) diphosphonate based on auxiliary ligand 2,2'-bipyridine

<p>The example of Co(II)-<i>N</i>-heterocyclic complex based on 1-hydroxyethylidenediphosphonic acid (H₅L = CH₃C(OH)(PO₃H₂)₂), namely [Co₂(H₃L)₂(2,2′-bipy)₂] <b>1</b>, has been solvothermally isolated using the second ligand 2,2'-bipyridine (2,2'-bipy) and characterized by powder X-ray diffraction (PXRD), elemental analysis, IR, and thermal gravimetric analyses. The single-crystal X-ray diffractions show that complex <b>1</b> possesses a 0-D structure built from binuclear unit [Co₂(O–P–O)₂] by μ₂-(O–P–O) bridge. Then, H-bonding and π–π stacking interactions further expand this 0-D structure into a 3-D supramolecular framework. Fluorescent measurements reveal that the maximum emission peak is centered at 421.5 nm, mainly deriving from intraligand π*–π transition state of the second ligand 2,2'-bipy (λ_em = 419.5 nm, λ_ex = 235 nm). Magnetism data indicate that <b>1</b> exhibits ferromagnetic behavior within binuclear Co(II) unit via μ₂-(O–P–O) bridge in <i>syn</i>-<i>anti</i> mode.</p