Solvothermal synthesis and crystal structures of two Holmium(III)-5-Hydroxyisophthalate entangled coordination polymers and theoretical studies on the importance of π•••π stacking interactions

Two new Ho(III)-5-hydroxyisophthalates with the formulae; {[Ho(hip)(H2O)(5)].(NO2).H2O} n (1) and {[Ho-4(hip)(4)(H2O)(20)].2(hip(2-)).8H(2)O}(n) (2) were solvothermally synthesized by self-assembly of Ho(III)-nitrate with rigid 5-hydroxyisophthalic acid (H 2 hip) linker. The coordination polymers (CPs) 1 and 2 crystallize in monoclinic P2(1)/c and P2(1)/n space groups, respectively. Both the CPs 1 and 2, shows 1D linear ladder shaped extension with the linkage having the backbone of hip(2-) moieties. In the both CPs 1 and 2, the Ho centers are nine coordinated. In CP 1, Ho shows distorted tricapped trigonal prismatic geometry while in CP 2, four Ho centres display three different geometries (monocapped square antiprismatic geometry around Ho1 and Ho3; distorted tricapped trigonal prismatic geometry around Ho-2 and; distorted monocapped square antiprismatic geometry around Ho4). The organic linker hip(2-) exhibits only one coordination mode (mu(2)-kappa O,O:kappa O,O). Theoretical calculations have been performed to analyze the antiparallel and parallel pi stacking interactions observed in the solid-state structures of coordination polymers1 and 2, respectively. The DFT study is focused on the energetic features of the pi-stacking, the influence of the ligand coordination to Ho upon the pi-stacking strength and their characterization by the noncovalent interaction plot (NCIplot) index computational tool. (C) 2022 Elsevier B.V. All rights reserved.