Engineering topics
Publications and source records attributed to Wilson, Chick C..
Short strong hydrogen bonds in multi-component organic acid molecular crystals exhibit temperature dependent proton migration for certain HB donor–acceptor distances.
Varying the electronic character of the acid co-former substituent group predictably alters weak and strong intermolecular interactions.
Atmospherically stable porous frameworks and materials are interesting for heterogeneous solid–gas applications. One motivation is the direct and selective uptake of pollutant/hazardous gases, where the material produces a measurable response in the presence of the analyte. In this report, we present a combined experimental and theoretical rationalization for the piezochromic response of a robust and porous molecular crystal built from an extensively fluorinated trispyrazole. The electronic response of the material is directly determined by analyte uptake, which provokes a subtle lattice contraction and an observable bathochromic shift in the optical absorption onset. Selectivity for fluorinated absorbates is demonstrated, and toluene is also found to crystallize within the pore. Lastly, we demonstrate the application of electronic structure calculations to predict a physicochemical response, providing the foundations for the design of electronically tunable porous solids with the chemical properties required for development of novel gas-uptake media.
The solid-state, low-temperature linkage isomerism in a series of five square planar group 10 phosphino nitro complexes have been investigated by a combination of photocrystallographic experiments, Raman spectroscopy and computer modelling. The factors influencing the reversible solid-state interconversion between the nitro and nitrito structural isomers have also been investigated, providing insight into the dynamics of this process. The cis-[Ni(dcpe)- (NO 2 ) 2 ] (1) and cis-[Ni(dppe)(NO 2 ) 2 ] (2) complexes show reversible 100% interconversion between the h 1 -NO 2 nitro isomer and the h 1 -ONO nitrito form when single-crystals are irradiated with 400 nm light at 100 K. Variable temperature photocrystallographic studies for these complexes established that the metastable nitrito isomer reverted to the ground-state nitro isomer at temperatures above 180 K. By comparison, the related trans complex [Ni(PCy 3 ) 2 (NO 2 ) 2 ] (3) showed 82% conversion under the same experimental conditions at 100 K. The level of conversion to the metastable nitrito isomers is further reduced when the nickel centre is replaced by palladium or platinum. Prolonged irradiation of the trans-[Pd(PCy 3 ) 2 (NO 2 ) 2 ] (4) and trans-[Pt(PCy 3 ) 2 (NO 2 ) 2 ] (5) with 400 nm light gives reversible conversions of 44 and 27%, respectively, consistent with the slower kinetics associated with the heavier members of group 10. The mechanism of the interconversion has been investigated by theoretical calculations based on the model complex [Ni(dmpe)Cl(NO 2 )].