Supramolecular arrangements of novel clickable 4-substituted 3,6-bis(2′-pyridyl)pyridazine molecules

Abstract

The clickable reaction between the starting 3,6-bis(2′-pyridyl)-1,2,4,5-tetrazine (bptz) with a series of terminal alkynes-containing functional biomolecules [prop-2-yn-1-ol, 4-(prop-2′-yn-1′-yl)morpholine and D-galactose] by means of an inverse electron demand Diels-Alder pathway has been studied and four new 4-substituted 3,6-bis(2′-pyridyl)pyridazine derivatives (4-Rdppn) were isolated, namely 4-(hydroxymethyl)-3,6-di(pyridin-2-yl)pyridazine (1), 4-((prop-2-yn-1-yloxy)methyl)-3,6-di(pyridin-2-yl)pyridazine (2) obtained by post-etherification reaction of 1, 4-(morpholinemethyl)-(3,6-dipyridin-2-yl)pyridazine monohydrate (3) and 3,6-di(pyridin-2-yl)-4-((2,2,7,7-tetramethyltetrahydro-5H-bis([1,3]dioxo)[4,5-b:4′,5′-d]pyran-5-yl)methoxy)methyl)pyridazine (4). The four new compounds were characterized by elemental analysis, IR spectroscopy and 1H/13C NMR and the crystal structures of 1–3 were solved by single crystal X-ray diffraction to elucidate their molecular structure. In the light of their structural knowledge, an analysis of the role of the substituent and steric effects on the crystal packing is carried out. Focusing on their dppn fragment of 1–3, an approximate s-trans/s-trans-conformation of the rings occurs as in the free dppn molecule and the bond lengths and angles agree with those reported for this molecule. π-π interactions and hydrogen bonds involving the substituents occur in 1 and 2. In addition, the water molecule of crystallization in 3 plays an important role in determining the crystal packing.