Coordination Polymers from Calixarene-Like [Cu₂(Dicarboxylate)₂]₄ Building Blocks: Structural Diversity via Atropisomerism

Abstract

The self-assembly of [Cu2(dicarboxylate)2]4 nanoscale secondary building units (nSBUs) into coordination polymers can occur in such a way that a range of calix-like atropisomers can exist. Eight compounds have been prepared and crystallographically characterized via reaction between Cu(NO3)2 and angular dicarboxylate ligands: {[Cu2(bdc)2(py)2]4•guest}n (1a), {[Cu2(bdc)2(py)2]4•4nitrobenzene•2EtOH}n (1b), {[Cu2(bdc)2(4-pic)2]4•4o-dichlorobenzene}n (2), {[Cu2(5-OEt-bdc)2(py)2]4•8H2O}n (3), {[Cu2(5-OPr-bdc)2(py)2]4•guest }n (4), {[Cu2(pdc)2(py)2]4•4MeOH}n (5), {[Cu2(pdc)2(4-pic)2]4•4H2O}n (6), and {[Cu2(tdc)2(MeOH)2]4•4naphthalene•8MeOH}n (7). The following atropisomers, all of which have also been observed in calixarenes, were observed: (a) cone (1a, 3, and 4); (b) partial cone (1b); (c) 1,2-alternate (2 and 5−7); and (d) 1,3-alternate (1a, 3, and 4). The similarities and differences between the crystal structures of 1−7 are detailed herein.