Quantum‐chemistry descriptors for photosensitizers based on macrocycles

Abstract

Studies on the synthesis, structure, spectroscopy and photodynamics of macrocycles such as porphyrin, phthalocyanine, and chlorin have increased in importance in the last decades. This interest is mainly due to their catalytic, spectrophotometric, magnetic, and electrochemical properties, which enable these compounds to be employed in many different applications. [1][2][3][4][5][6] In combination with experimental approaches, theoretical studies based on quantum mechanics are useful for the comprehension of electronic structure and environmental effects. [2,[7][8][9][10][11][12][13][14][15][16][17][18] There are two main methodologies that aim to increase the efficiency for energy transfer appliances: complexation with different metallic ions and the addition of (a) polar/(un)charged substituents. Both methodologies are able to avoid the aggregation and/or enhance the substrate interaction while maintaining or even improving photochemical properties.[2,7-9,19-33]One of the first ab initio studies for porphyrins [34] was performed through the MO-LCGO-SCF method, described by Roothaan. [35][36][37] Since then, the number of ab initio studies for these macrocycles has grown significantly, particularly concerning the calculations based on density functional theory (DFT), due to its good relation and cost/accuracy ratio. [2,8,9,[17][18][19][20][21][22][23]25,26,28,29,31,[38][39][40][41][42][43][44][45][46][47] DFT studies of most porphyrins and phthalocyanines have employed B3LYP functio nal; [2,8,9,25,28,[38][39][40]48] nevertheless, other functionals such as BLYP, [8,29,49] VWN-B-P, [26] and BHandHLYP [8] have also been used. T. E. Shubina and T. Clark [25] performed a methodological study for porphyrins complexed to Fe(III) and Co(II), which indicated that B3LYP and OLYP functionals are excellent choices for studying these macrocycles. Time-dependent Hartree-Fock, [26,38,[41][42][43] ZINDO/S, [38,42] configuration interaction, [41,42] and CASSCF/CASPT2Phthalocyanines, porphyrins, and chlorins have been widely studied as photosensitizers. Both experimental and computational strategies are employed in order to propose new and more active molecules derived from those macrocycles. In this context, there are two main strategies used: (i) the addition of different substituents and (ii) the complexation of the macrocycle with different metallic ions. In this work, we present selected descriptors based on quantum chemistry calculations for forty macrocycles, including some approved drugs. We have found that density functional theory is a suitable methodology to study the large sets of molecules when applying the B3LYP/LanL2DZ methodology for geometry optimization and TD-OLYP/6-31G(d) for absorption spectrum. The inclusion of solvent effects by means of continuum model is important in order to obtain the accurate electronic data. We have verified that by bonding charged or polar substituents to the macrocycle, it is possible to enhance water solvation as well as to improve spectroscopic properties because molecular orbital...

CAHM1: A Theory-Based Proposal for a New DSSC D–A−π–A Dye

“…It is important to mention that the DFT results tend to overestimate the absorption wavelength. It is well known that for macrocycles, such as porphyrins and phthalocyanines, this overestimation is around 10–15% (see, e.g., de Visser and Bettanin). Therefore, the absolute values of the obtained absorption spectra should be considered with caution; the overall picture of the transitions, however, is acceptable.…”

Improving the Photocatalytic Hydrogen Generation Using Nonaggregated Zinc Phthalocyanines

“…The required input files were prepared, and the postprocessing procedures were accomplished by using GaussView (v5.0.8), IboView (v20150427), and Chemcraft (v1.8) as the front-end visualization programs. Accordingly, the ground-state geometries were optimized with no symmetry restrictions by applying density functional theory (DFT) with B3LYP hybrid functional at the relativistic effective core potential basis set of double-ζ quality, LANL2DZ (Los Alamos National Laboratory 2 Double-Zeta), which has been proven adequate for the geometry predictions of the macrocyclic metal complexes possessing a cavity for PC reactions …”

Application of TD-DFT Theory to Studying Porphyrinoid-Based Photosensitizers for Photodynamic Therapy: A Review

“…Bettanin et al also searched for the best descriptors of the photodynamic activity of porphyrin, phthalocyanine, and chlorin [ 94 ]. They proposed molecular volume, LUMO energy, oscillator strength, dipole moment, and free energy of solvation as the most relevant for the desired activity.…”