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Two isostructural lanthanide-based metal - organic frameworks, {[Ln(C16H12N2O4)(CHO2)(OH2)·2(C5H11NO)]}n, Ln = Yb (1) and Tm (2), and a cadmium(II) coordination polymer,{[Cd2(C16H12N2O4)(NO3)·4(C3H7NO)]}n, were synthesized by the combination of the respective metal nitrate and 2,2′-diamino-trans 4,4′-stilbenedicarboxylate (C16H12N2O4) under solvothermal conditions [C5H11NO = diethylformamide and C3H7NO = dimethylformamide]. Their structures were determined by X-ray single crystal analysis, X-ray powder diffraction, Fourier transformed infrared spectroscopy, elemental analysis, thermogravimetric analysis and solid state photoluminescence spectroscopy. Both lanthanide structures are infinite three-dimensional non-penetrating networks with extremely large diamond shape accessible channels of cross-sectional dimensions [30 A x 12 A] and with the amino-functional groups projecting into the channels. The cadmium-based structure is a one-dimensional coordination polymer with both the carboxylate and the amino groups coordinating the cadmium atoms, which resulted in a large increase in the rigidity of the ligand. Ligand-based fluorescence was exhibited by all three networks, with the cadmium based structure showing the highest intensity and longest fluorescence radiative lifetime.

Three coordination polymers were synthesized from pyrazine-2,3,5,6-tetracarboxylic acid (H 4 pztc) in combination with calcium, zinc and manganese ions under hydrothermal conditions and their structures were determined by single crystal X-ray diffraction, powdered X-ray diffraction, Fourier transformed infrared spectroscopy, thermogravimetric and elemental analyses. Structure 1 , {(Ca(H 2 pztc)(H 2 O) 3 ) n , crystallizes as 1-D chains, with the partially deprotonated ligand in –O,N,O– coordination mode and with the Ca atoms in an uncommon nine coordinate environment. Structure 2 , {Zn1(pztc)(H 2 O) 2 Zn2(H 2 O) 4 } n , is an infinite, 2-D coordination network that contains two nonequivalent Zn atoms, each with octahedral geometry, and the fully deprotonated pztc 4− in bis -bridging chelating coordination mode. The stacked 2-D layers are stabilized by extensive inter-layer water-carboxylate hydrogen-bonding with an inter-layer distance of 4.9 A. Structure 3, {(Mn 2 (pztc)(H 2 O) 2 )} n , is a covalently bonded 3-D network containing two nonequivalent Mn atoms, each with octahedral geometry, and the fully deprotonated pztc 4− units. Structure 3 exhibits paramagnetic behavior at room temperature, and weak antiferromagnetic properties at very low temperature, which is consistent with their nearest Mn…Mn separation distance of 4.9 A.

Four anthracene-based lanthanide metal-organic framework structures (MOFs) were synthesized from the combination of the lanthanide ions, Eu3+, Tb3+, Er3+, and Tm3+, with 9,10-anthracenedicarboxylic acid (H2ADC) in dimethylformamide (DMF) under hydrothermal conditions. The 3-D networks crystalize in the triclinic system with P-1 space group with the following compositions: (i) {{[Ln2(ADC)3(DMF)4·DMF]}n, Ln = Eu (1) and Tb (2)} and (ii) {{[Ln2(ADC)3(DMF)2(OH2)2·2DMF·H2O]}n, Ln = Er (3) and Tm (4)}. The metal centers exist in various coordination environments; nine coordinate in (i), while seven and eight coordinate in (ii). The deprotonated ligand, ADC, assumes multiple coordination modes, with its carboxylate functional groups severely twisted away from the plane of the anthracene moiety. The structures show ligand-based photoluminescence, which appears to be significantly quenched when compared with that of the parent H2ADC solid powder. Structure 2 is the least quenched and showed an average photoluminescence lifetime from bi-exponential decay of 0.3 ns. On exposure to ionizing radiation, the structures show radioluminescence spectral features that are consistent with the isolation of the ligand units in its 3-D network. The spectral features vary among the 3-D networks and appear to suggest that the latter undergo significant changes in their molecular and/or electronic structure in the presence of the ionizing radiation.