Coordination Polymers of Calcium with the Redox-Active Acenaphthene-1,2-diimine Ligand

The reactions of the calcium acenaphthene-1,2-diimine complex [(Dpp-Bian)Ca-2-(2+)(THF)(4)] (Dpp-Bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with phenazine (Phz) in tetrahydrofuran (THF) and with 4,4'-bipyridine (4,4'-Bipy) in benzene proceed with the electron transfer from Dpp-Bian(2-) to the substrates to give dimer [(Dpp-Bian)Ca-1-(2+)(Phz)(1-)(THF)](2)& BULL;6(THF) (I) and 2D coordination polymer [(Dpp-Bian)Ca--(2+)(4,4'-Bipy)(-)(4,4'-Bipy)(0.5)]& BULL;3(C6H6) (II), respectively. The reaction of [(Dpp-Bian)Ca-2-(2+)(THF)(4)] with 1,3-bis(4-pyridyl)propane (Bpp) in a THF/benzene mixture is not accompanied by the electron transfer and leads to the formation of 2D coordination polymer [(Dpp-Bian)Ca-2-(2+)(Bpp)(2)]& BULL; 2(THF)& BULL;(C6H6) (III). Compounds I-III are characterized by elemental analysis and IR spectroscopy. The molecular structure of compound I is determined by XRD (CIF file CCDC no. 2176826). The quality of the XRD experimental data obtained for crystals of compounds II and III turns out to be insufficient for the determination (with a necessary accuracy) of bond lengths and angles. The XRD data make it possible to establish unambiguously the mutual arrangement of atoms in the molecules of compounds II and III and the number and mutual arrangement of solvate benzene and THF molecules. The presence of ligand-localized unpaired electrons in compounds I-III is confirmed by EPR spectroscopy. The thermal stability of coordination polymers II and III is studied by thermogravimetric analysis.

Automated summary

The reactions of a calcium acenaphthene-1,2-diimine complex with phenazine and 4,4'-bipyridine result in electron transfer and the formation of dimer and coordination polymer, respectively. However, the reaction with 1,3-bis(4-pyridyl)propane leads to the formation of another coordination polymer without electron transfer. The compounds are characterized by various analytical techniques, and the presence of ligand-localized unpaired electrons is confirmed.