Discrete and polymeric complexes of a macrocyclic pillar ligand in the absence and presence of dicarboxylic acid coligands

Abstract

a The macrocyclic pillar ligand, dipyridyldibenzotetraaza[14]annulene (H2L), in the absence and presence of the dicarboxylate coligands, biphenyl-4,4′-dicarboxylic acid (H2bpdc) or benzene-1,3-dicarboxylic acid (H2bdc), reacts with nickel(II), cobalt(II), and zinc(II) to yield [Ni(L)] (1), [Co(L)] (2), [Co(L)]n (3), {[Zn(H2L)(bdc)]•0.5DMF•1.5H2O}n (4), and {[Co4(L)2(bpdc)2]•2DMF•H2O}n (5) displaying both discrete and polymeric structures. Complexes 1 and 2 are isostructural, with the respective low-spin, square-planar metal ions occupying the macrocyclic cavity and bound to the N4-donor set of the macrocycle in its doubly deprotonated form. In 3, the cobalt(II) centre again occupies the macrocyclic cavity, but in this case one axial site is occupied by a pyridyl nitrogen from a second ligand complex, resulting in the formation of an infinite zigzag one-dimensional (1D) structure. Solvothermal reaction between Zn(NO3)2•4H2O, H2L and H2bdc afforded the 2D coordination polymer {[Zn(H2L)(bdc)]•0.5DMF•1.5H2O}n (4) in which H2L ligands crosslink 1D (bdc-Zn)n wavy backbones via Zn-Npyd bonds. In contrast, the solvothermal reaction of H2L with Co(NO3)2•6H2O in the presence of H2bpdc resulted in formation of the 2-fold interpenetrated 3D coordination polymer, {[Co4(L)2(bpdc)2]•2DMF•H2O}n (5), exhibiting a pillaredlayer structure. The 3D framework of 5 is based on dicobalt(II) cluster secondary building units (SBUs) to yield a rob net in which the bpdc/Co-based 2D nets are cross-linked by CoL macrocyclic pillar units; the framework of 5 is thermally stable until 350 °C.

Synthesis, functionalization and coordination chemistry of dibenzotetraaza[14]annulenes

“…The solid-state photoluminescence spectrum of H260 clearly displays a broad emission centre at 655 nm with an excitation peak at 365 nm. However, no emission peaks were observed for 61, 62 and 68 relative to H260 due to the energy loss by non-radiative decay [70]. A similar methodology was also described by Ramle et al [3,73] who diversified and extended the π-conjugation system of indoleninyl-DBTAA framework (Figure 13).…”

“…X-ray crystallography on 63 reveals the presence of a coordination polymer (Figure 10a). The cobalt(II) atom is tetra-coordinated within the ring cavity and extends its coordination number to five with a square-pyramidal geometry by connecting to a pyridylnitrogen atom of a symmetry related molecule to generate a one-dimensional helical chain [70].…”