Abstract
Supramolecular chemistry is the useful tool for establishing the understanding on the
functioning of many existing or new materials. This study describes the solid-state
organic transformation of olefins to cyclobutane-linked photoadducts in a form of neat
ligands and co-crystals using UV light. We therefore have grown single crystals of the
synthesised two carboxylic acids derivatives and two co-crystals using two bipyridyl
derivatives.
The first phase of the study involved the synthesis of organic ligands derivatives: (E)-
4-oxo-6-phenylhex-5-enoic acid (Form 1) and (E)-4-oxo-6-pyridylhex-5-enoic acid
(Form 2) using Claisen-Schmidt condensation reaction. The molecular structures of
the synthesised organic ligands were confirmed by proton (1H) and carbon-13 (13C)
nuclear magnetic resonance spectroscopy (NMR) and single crystal X-ray diffraction
(SCXRD) analysis. The Fourier Transform inferred (FTIR) spectroscopy confirmed the
expected chemical functionalities present within the synthesised organic ligands. The
X-ray crystal structures have shown that the trans-alkene conformation was adopted
in both organic ligands.
In the second phase of our study, we utilised crystal engineering strategies to prepare
multi-component co-crystals by employing carboxylic acid and pyridyl
moieties/synthons. The mechanosynthesis protocol for the design of co-crystals was
employed using liquid-assisted grinding (LAG). The mole ratios of 2:1 were kept the
same during the synthesis of (E)-4-oxo-6-phenylhex-5-enoic acid: 2-bis(4’-
pyridyl)ethane (Form 1: BPA) and Nitrate: 2-bis(4’-pyridyl)ethene (NO3
-: BPE2+). Both
the X-ray crystal structures indicated that the neighbouring molecules interacts
strongly by hydrogen bonds.
In overall, the employed synthetic strategies were successfully to achieve the
envisaged arrangement of the carbon-carbon double bonds for neat ligands and cocrystals.
The crystal structures revealed the minimum distance of close contacts for
carbon-carbon double bonds to allow cycloaddition reaction in the solid state. Single
crystal to single crystal (SCSC) transformation was impractical. However, the
alternative route to cycloaddition reaction on the powdered form of these organic ...