Azobenzene-Iron(III)porphyrin Hybrid Composite as a Light-Driven Molecular Spin Regulator: Some Promising Insights from DFT

The photo-isomerization of azobenzene (AZB) provides the essential stimulation for the controlled regulation of spin-crossover in the iron(III)porphyrin complex. We have performed theoretical simulations to predict the strategic design of a modular material via attachment of azobenzene to the iron(III) center. The light-induced isomerization of azobenzene triggers a cascade of electronic changes resulting from a low to a high-spin transition in the electronic configurations of Fe(III) ions. In principle, the successive conformational changes in AZB exert considerable distortion on the iron coordination sphere, subsequently changing the crystal field splitting pattern. The light-induced rotatory motion of AZB is the necessary driving force to manipulate the spin state of the Fe(III) ion. The density functional theory-based calculations on the 2D extended porphyrin array and its coupling to AZB molecules affirm considerable changes in the electronic properties of the system. The consequence of light-induced isomerization in azobenzene effectively modulates the electronic transport behavior of the system in the two different spin states. This was checked through the calculations of transmission, conductance, and IV characteristics. The comprehensive spectral simulations manifest a reasonable correlation to the predicted spin crossover in the system, with clear evidence provided by the transport properties.