Is Molecular Chirality Connected to Supramolecular Chirality? The Particular Case of Chiral 2‑Pyridyl Alcohols

Ten structurally related racemic 2-pyridylmethyl alcohols containing an <i>o</i>-carborane core (1,2-<i>closo-</i>C₂B₁₀H₁₀; <i>rac-</i><b>1a</b>) or <i>m</i>-carborane (1,7-<i>closo-</i>C₂B₁₀H₁₀; <i>rac-</i><b>2a</b>) or <i>p</i>-carborane (1,7-<i>closo-</i>C₂B₁₀H₁₀; <i>rac-</i><b>3a</b>) and their enantiopure forms (<i>R-</i> and <i>S-</i><b>1a</b> or <i>R-</i> and <i>S-</i><b>2a</b> or <i>R-</i> and <i>S-</i><b>3a</b>), as well as an iodo derivative of <i>rac-</i><b>3a</b> (<i>rac-</i><b>4a</b>) and a non-carborane derivative (C₆H₅; <i>rac-</i><b>5</b>) have been studied by single crystal X-ray crystallography. All racemic and enantiopure structures show O–H···N hydrogen bonded homochiral 2₁-helical networks, except that for <i>rac-</i><b>3a</b>, which forms O–H···N hydrogen bonded trimers. A comparison of these X-ray structures with that for others found in the Cambridge Structural Database for chiral 2-pyridyl alcoholseither in racemic or enantiopure formsthat form O–H···N hydrogen bonded homochiral 2₁-helical networks reveals a possible relationship between the torsion angle of the hydrogen bond donor and acceptor groups in these molecules and the hydrogen bonded supramolecular helices formed in the solid state