Enantiomers of conformation-flexible cyclopentane-1,2,3,4-tetracarboxylate in metal–organic frameworks

• Published in: CrystEngComm 2010-01, Vol.12 (12), p.4416-4423
• Main Authors: Yao, Ru-Xin, Hao, Zheng-Ming, Guo, Cai-Hong, Zhang, Xian-Ming
• Format: Article
• Language: English
• Subjects: Bonding; Coordination polymers; Density functional theory; Enantiomers; Ligands; Mathematical analysis; Metal-organic frameworks; Pillars; Three dimensional
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/c0ce00144a

Four novel coordination polymers, [Mn2(cptc)(2,2[prime or minute]-bpy)(H2O)][middle dot]H2O (1), [Mn2(cptc)(phen)(H2O)][middle dot]H2O (2), Mn4(cptc)2(phen)4(H2O)2][middle dot]3H2O (3) and [Cd2(cptc)(H2O)3] (4) (H4cptc = cyclopentane-1,2,3,4-tetracarboxylic acid, 2,2[prime or minute]-bpy = 2,2[prime or minute]-bipyridine, phen = 1,10-phenanthroline), have been synthesized by hydrothermal reactions of flexible (1S,2S,3R,4R)-H4cptc with MnCl2/CdCl2. By breaking the mirror plane of symmetry, the meso-cptc ligand is successfully converted into two pairs of enantiomers, the (1R,2S,3S,4R)- and (1S,2R,3R,4S)-cptc groups in 1-3 are unprecedented while the documented (1R,2R,3R,4S)- and (1S,2S,3S,4R)-cptc enantiomers exhibit an unprecedented [small mu ]6-mode in 4. Layered 1 and 2 show similar structures and are constructed by centrosymmetric tetranuclear units. 3 is a binodal (3,4)-connected layer with Schlafli symbols of (53)2(54[middle dot]82), in which cptc exhibits two types of [small mu ]5-mode bonding. 4 has a 3-D pillar layered structure composed of neutral [Cd(cptc)]n layers and octahedral CdO6 pillars. The presence probability of different enantiomers is in agreement with the relative stability of different conformations of cptc calculated by time-dependent density functional theory (TD-DFT).