title: Absorption Spectra of the Potential Photodynamic Therapy Photosensitizers Texaphyrins Complexes:  A Theoretical Analysis.
abstract: A systematic study of a class of divalent transition-metal texaphyrin complexes (M-Tex(+), M = Mn, Fe, Co, Ni, Cu, Zn), recently proposed as active photosensitizers in photodynamic therapy (PDT), was undertaken for the ground and excited electronic states. Geometry optimizations were performed by using the PBE0 exchange-correlation functional coupled with the 6-31G(d) basis set, while electronic excitations energies were evaluated by means of time-dependent density functional response theory (TD-DFT) at the PBE0/6-31+G(d) // PBE0/6-31G(d) level of theory. Solvent effects on excitation energies were taken into account in two ways:  by considering solvent molecules explicitly coordinated to the metal center and as bulk effects, within the conductor-like polarizable continuum model (C-PCM). The influence of the metal cation on the so-called Q-band, localized in the near-red visible region of the spectrum, was carefully examined since it plays a basic role in the drug design of new photodynamic therapy photosensitizers. The differences between experimental and computed excitation energies were found to be within 0.3 eV.
authors.affiliation: Dipartimento di Chimica and Centro di Calcolo ad Alte Prestazioni per Elaborazioni Parallele e Distribuite-Centro d'Eccellenza MURST, Università della Calabria, I-87030 Arcavacata di Rende, Italy, and Dipartimento di Chimica, Università degli Studi della Basilicata, Via Nazario Sauro, 85, 85100 Potenza.
authors.forename: Angelo Domenico
authors.initials: AD
authors.lastname: Quartarolo
authors.affiliation: Dipartimento di Chimica and Centro di Calcolo ad Alte Prestazioni per Elaborazioni Parallele e Distribuite-Centro d'Eccellenza MURST, Università della Calabria, I-87030 Arcavacata di Rende, Italy, and Dipartimento di Chimica, Università degli Studi della Basilicata, Via Nazario Sauro, 85, 85100 Potenza.
authors.forename: Nino
authors.initials: N
authors.lastname: Russo
authors.affiliation: Dipartimento di Chimica and Centro di Calcolo ad Alte Prestazioni per Elaborazioni Parallele e Distribuite-Centro d'Eccellenza MURST, Università della Calabria, I-87030 Arcavacata di Rende, Italy, and Dipartimento di Chimica, Università degli Studi della Basilicata, Via Nazario Sauro, 85, 85100 Potenza.
authors.forename: Emilia
authors.initials: E
authors.lastname: Sicilia
authors.affiliation: Dipartimento di Chimica and Centro di Calcolo ad Alte Prestazioni per Elaborazioni Parallele e Distribuite-Centro d'Eccellenza MURST, Università della Calabria, I-87030 Arcavacata di Rende, Italy, and Dipartimento di Chimica, Università degli Studi della Basilicata, Via Nazario Sauro, 85, 85100 Potenza.
authors.forename: Francesco
authors.initials: F
authors.lastname: Lelj