Crystal engineering of a series of complexes and coordination polymers based on pyrazole-carboxylic acid ligands

Abstract

Three new complexes namely [Cu(L1)H₂O]·2H₂O (1), [Cu₂(L4)₂(DMF)₂(H₂O)₂](NO₃)₂ (4) and [{Cd₂(L4)₂Cl₂(DMF)₂}] (5), and two coordination polymers namely [Co(μ-L2)(DMF)₂]·2H₂O (2) and [Co(μ-L3)(DMF)₂]·H₂O (3) have been synthesized from a series of pyrazole-carboxylate ligands namely 1,1′-(ethane-1,2-diyl)bis(5-methyl-1H-pyrazole-3-carboxylic acid) (H₂L1), 1,1′-(oxybis(ethane-2,1-diyl))bis(5-methyl-1H-pyrazole-3-carboxylic acid) (H₂L2), 1,1′-(butane-1,4-diyl)bis(5-methyl-1H-pyrazole-3-carboxylic acid) (H₂L3), and 2-(1′,5,5′-trimethyl-1H,1′H-[3,3′-bipyrazol]-1-yl)acetic acid (H₂L4), and Cu^II/Cd^II/Co^II ions. Single crystal structures of these compounds are discussed in the context of the effect of conformation of the ligands and supramolecular interactions observed within these edifices. Temperature-dependent magnetic data of 4 could be fitted best using two non-interacting Cu^II ions (S = 1/2) per molecule with g_iso = 2.28 and a temperature-independent paramagnetism, TIP = 1.75 × 10⁻⁵ cm³ mol⁻¹.