K. Tang, Jianjun Zhang, Da-hai Zhang
2013
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0
Influential Citations
19
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Journal
The Journal of Chemical Thermodynamics
Abstract
A series of lanthanide complexes with the 2-chloro-4,5-difluorobenzoate (2-cl-4,5-dfba) and 1,10-phenanthroline (phen), have been synthesized with the formulae of [La(2-cl-4,5-dfba) 3 phen] n · n H 2 O (1), [Nd(2-cl-4,5-dfba) 3 phenH 2 O] 2 (2), [Ln(2-cl-4,5-dfba) 3 phen] 2 (Ln = Eu (3), Ho (4)). The complexes are characterized by elemental analysis, infrared and fluorescent spectra and X-ray single-crystal diffraction. The structures of the four complexes are very different. Complex 1 is an infinite 1D chain polymeric structure formed by the asymmetric units with the mirror growth pattern. Each La 3+ ion is coordinated to four bridging carboxylic groups, two tridentate chelating–bridging carboxylic groups, simultaneous with one phen molecule, giving the coordination number of nine. In the molecular structures of complexes 2 and 3, two Ln 3+ ions are linked by four carboxyl groups, forming two binuclear molecules. In addition, each Nd 3+ ion in complex 2 is bonded to one H 2 O molecule and one carboxyl group by monodentate mode, one phen molecule by bidentate chelating, and each Eu 3+ ion is also chelated to one phen molecule and one carboxyl group in complex 3. And in complex 4, the Ho 3+ ion yields a eight-coordinated distorted square anti-prism coordination geometry. The three-dimensional IR accumulation spectra of gaseous products for complexes 1 to 4 are analyzed and further authenticated the thermal decomposition processes with TG-DTG curves. The heat capacities of complexes 2 to 4 are measured and fitted to a polynomial equation by the least squares method on the basis of the reduced temperature x ( x = [ T −( T max + T min )/2]/[( T max − T min )/2]). Then the smoothed molar heat capacities and thermodynamic functions of complexes 2 to 4 are calculated. The fluorescence intensity of complex 3 is markedly improved as well.