Seven novel coordination polymers constructed by rigid 4-(4-carboxyphenyl)-terpyridine ligands: synthesis, structural diversity, luminescence and magnetic properties

Abstract

Seven coordination polymers, namely [Mn(4-cptpy)₂]_n (1), [Co(4-cptpy)₂]_n (2), [Mn₃(4-cptpy)₆(H₂O)]_n·2nH₂O (3), [Co(4-cptpy)(HCOO)(H₂O)]_n·nDMF (4), [Zn₂(4-Hcptpy)₂Cl₄]_n·2nC₂H₅OH·nH₂O (5), [Co₄(3-cptpy)₄(HCOO)₄(H₂O)₂]_n (6), and [Mn(3-cptpy)₂]_n (7) (4-Hcptpy = 4-(4-carboxyphenyl)-4,2′:6′,4′′-terpyridine; 3-Hcptpy = 4-(4-carboxyphenyl)-3,2′:6′,3′′-terpyridine), have been synthesized under hydro(solvo)thermal conditions and structurally characterized. A general solvothermal method is proposed for preparing carboxylate complexes in DMF solution without any basic additive. 1 and 2 possess isostructural 3D metal–organic frameworks containing nanosized cavities. 3 is a beautiful 2D coordination polymer assembled by flower-like Mn₃(4-cptpy)₆(H₂O) subunits. 4 and 6 both display 2D polymeric networks constructed from 4/3-cptpy⁻ ligands, in which the formate ligands originate from the hydrolysis of DMF. 5 is a 1D 2₁ helical chain polymer. 7 shows a 2D network with a (3.6) two-nodal kgd topology. 4/3-Hcptpy ligands display seven types of coordination modes. The zinc complex 5 emits strong violet luminescence. 1 and 2 are both thermally stable below 440 °C and exhibit antiferromagnetic interactions.