Luminescent cadmium 5-sulfoisophthalate dipyridylpiperazine coordination polymers with ladder, interpenetrated binodal net, or nanotube-embedded layer topologies

Abstract

The conformationally flexible dipyridyl ligands bis(3-pyridylmethyl)piperazine (3-bpmp), bis(4-pyridylmethyl)piperazine (4-bpmp) and bis(4-pyridylmethyl)homopiperazine (4-bpmh) have been utilized to prepare the cadmium 5-sulfoisophthalate (sip) coordination polymers {[Cd2(sip)2(3-bpmpH2)(H2O)4]·19H2O}n (1), {[Cd2(sip)2(4-bpmpH2)(4-bpmp)]·4H2O}n (2), and {[Cd(sip)(4-bpmhH)]·11H2O}n (3). Compound 1 possesses 1D ladder motifs with parallel [Cd(sip)]nn− chains strutted by doubly protonated 3-bpmpH22+ rungs. [Cd(sip)]nn− ribbons with bound sip sulfonate groups are present in both 2 and 3, but different geometric dispositions of the pyridyl arms of the tethering ligands effect a variance in dimensionality. The “linear” 4-bpmpH ligands in 2 link [Cd(sip)]nn− ribbons into a 3-fold interpenetrated 3,5-connected binodal 3D lattice with (426)(426583) topology. In contrast, pairs of curled 4-bpmhH ligands in 3 connect [Cd(sip)]nn− ribbons into a unique 2,3,5-trinodal looped network with (4)(426)(436.84102) topology. The ligand-pair loops bracket water-filled one-dimensional (1-D) elliptical nanotubules. All materials exhibited blue or violet emission upon irradiation with ultraviolet light.