Structural influence of the length and functionality of N,N-donor spacers in Cd(II) ladder-type coordination polymers

The understanding of the effect generated by small differences of the organic ligands on the molec-ular and supramolecular arrangement of coordination polymers (CPs) is a key factor to control their properties. Therefore, the study of structurally related ligands differing in some factors inter alia func-tional group orientation, length, or functionality is a crucial task for crystal engineers. In this contribu-tion, the reactions between Cd(OAc)2middot2H2O, alpha-acetamidocinnamic acid (HACA) and different N,N-donor spacers with increasing length (pyrazine, pyz; 4,4'-bipyridine, 4,4'-bipy; 1,2-bis(4-pyridyl)ethylene, 1,2-bpe), as well as additional functionalities (4,4'-azopyridine, 4,4'-azpy) have been successfully performed. Their crystal structures have been elucidated revealing a family of ladder-type 1D CPs showing molec-ular arrays with single pillars for {[Cd2( mu-ACA)2(ACA)2(pyz)(H2O)2] middot2EtOH}n ( 1 ), and double pillars for [Cd2(mu-ACA)2(ACA)2(4,4'-bipy)2]n ( 2 ), [Cd2(mu-ACA)2(ACA)2(1,2-bpe)2]n ( 3 ) and {[Cd2(mu-ACA)2(ACA)2(4,4'-azpy)2] middot4,4'-azpy middot9H2O}n ( 4 ). Remarkably, the effect of the addition of the azo group in 4 compared with 2 and 3 has led to a CP with the same molecular arrangement but different crystal packing, allowing the introduction of one non-coordinated 4,4'-azpy and nine water molecules. Finally, their solid-state UV-Vis and photoluminescence have been measured observing their blue-emitting properties.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )