REGULAR ARTICLE Integrated computational approaches for spectroscopic studies of molecular systems in the gas phase and in solution: pyrimidine as a test case Malgorzata Biczysko • Julien Bloino • Giuseppe Brancato • Ivo Cacelli • Chiara Cappelli • Alessandro Ferretti • Alessandro Lami • Susanna Monti • Alfonso Pedone • Giacomo Prampolini • Cristina Puzzarini • Fabrizio Santoro • Fabio Trani • Giovanni Villani Received: 24 July 2011 / Accepted: 3 March 2012 / Published online: 8 April 2012 Ó Springer-Verlag 2012 Abstract An integrated computational approach built on quantum mechanical (QM) methods, purposely tailored inter- and intra-molecular force fields and continuum sol- vent models combined with time-independent and time- dependent schemes to account for nuclear motion effects is applied to the spectroscopic investigation of pyrimidine in the gas phase as well as in aqueous and CCl 4 solutions. Accurate post-Hartree–Fock methodologies are employed to compute molecular structure, harmonic vibrational fre- quencies, energies and oscillator strengths for electronic transitions in order to validate the accuracy of approaches rooted into density functional theory with emphasis also on hybrid QM/QM 0 models. Within the time-independent approaches, IR spectra are computed including anharmo- nicities through perturbative corrections while UV–vis line-shapes are simulated accounting for the vibrational structure; in both cases, the environmental effects are described by continuum models. The effects of confor- mational flexibility, including solvent dynamics, are described through time-dependent models based on pur- posely DFT-tailored force fields applied to molecular dynamics simulations and on QM computations of spec- troscopic properties. Such procedures are exploited to Dedicated to Professor Vincenzo Barone and published as part of the special collection of articles celebrating his 60th birthday. Electronic supplementary material The online version of this article (doi:10.1007/s00214-012-1201-3) contains supplementary material, which is available to authorized users. M. Biczysko (&)  J. Bloino  G. Brancato  G. Prampolini Scuola Normale Superiore di Pisa Piazza dei Cavalieri 7, 56126 Pisa, Italy e-mail: malgorzata.biczysko@sns.it Present Address: M. Biczysko Center for Nanotechnology Innovation @NEST, Istituto Italiano di Tecnologia, Piazza San Silvestro 12, 56127 Pisa, Italy Present Address: J. Bloino CNR–Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), UOS di Pisa, Area della Ricerca, via G. Moruzzi 1, 56124 Pisa, Italy I. Cacelli  C. Cappelli Dipartimento di Chimica e Chimica Industriale, Universita ` degli Studi di Pisa, Via Risorgimento 35, 56126 Pisa, Italy A. Ferretti  A. Lami  S. Monti  F. Santoro  G. Villani CNR, Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), UOS di Pisa, Area della Ricerca, via G. Moruzzi 1, 56124 Pisa, Italy A. Pedone Dipartimento di Chimica, Unversita ` di Modena e Reggio Emilia, Via G. Campi 183, 41125 Modena, Italy Present Address: G. Prampolini CNR, Consiglio Nazionale delle Ricerche, Istituto per i Processi Chimico-Fisici (IPCF-CNR), UOS di Pisa, Area della Ricerca, via G. Moruzzi 1, 56124 Pisa, Italy C. Puzzarini Dipartimento di Chimica ‘‘G. Ciamician’’, Universita ` di Bologna, Via F. Selmi 2, 40126 Bologna, Italy F. Trani CECAM, Centre Europe ´en de Calcul Atomique et Mole ´culaire, EPF Lausanne, Batochime (BCH), 1015 Lausanne, Switzerland 123 Theor Chem Acc (2012) 131:1201 DOI 10.1007/s00214-012-1201-3