Mechanistic Investigation of the Synthesis of Dianionic In-Derived Coordination Polymers.

The mechanism of formation of crystalline coordination polymers is as complex as the architectures themselves. In this Communication, we detail a three-tiered approach using density functional theory (DFT) analysis, synthesis, and in situ Raman spectroscopy to study the formation of coordination polymers. Specifically, the previously reported coordination polymers YCM-22 and YCM-51 containing the [In(CO 2 R) 2 X 3 ] 2- (X = halogen) molecular building unit (MBU) were investigated. DFT revealed two potential pathways of formation, involving the initial formation of either [InCl 4 ] - or [In(CO 2 R)Cl 3 ] - . A molecular dimeric In species ( 8a ) containing two [In(CO 2 R)Cl 4 ] 2- centers bridged by 2,5-thiophenedicarboxylic acid was isolated. When a suspension of 8a was treated with a solution of 2,5-thiophenedicarboxylic acid, an isomer of the coordination polymer YCM-22 (denoted as YCM-22') was formed. In situ Raman analysis of the formation of YCM-22 confirms that [InCl 4 ] - forms at the onset of the reaction and that the [In(CO 2 R) 2 X 3 ] 2- MBU forms at its expense. The totality of the data presented support a mechanism of formation of one-dimensional In-derived coordination polymers and present a roadmap for future investigations into the formation of other crystalline coordination polymers.