Christopher Farley1,2, Amit Aggarwal3, Sunaina Singh3, Aaron Dolor4, Philip To1, Alexander Falber5, Maxwell Crossley6, Charles Michael Drain1,7. 1. Department of Chemistry, Hunter College of the City University of New York, New York, New York, 10065. 2. Department of Chemistry, The Graduate Center of the City University of New York, New York, New York, 10016. 3. Department of Natural Sciences, LaGuardia Community College of the City University of New York, Long Island City, New York, 11101. 4. Department of Bioengineering, Therapeutic Sciences and Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, 94143. 5. School of Chemistry, The University of New South Wales, Sydney, New South Wales, 2052, Australia. 6. School of Chemistry, The University of Sydney, Sydney, New South Wales, 2006, Australia. 7. The Rockefeller University, New York, New York, 10065.
Abstract
Nitro-porphyrins are an important class of commercial dyes with a range of potential applications. The nitro group is known to dramatically affect the photophysics of the porphyrin, but there are few systematic investigations of the contributing factors. To address this deficiency, we present spectroscopic studies of a series of nitro-porphyrins, accompanied by density functional theory calculations to elucidate their structures. In particular, we explore how the positions of the substituents affect the energy levels and nuclear geometry. As expected, nitro groups on the meso-phenyl rings cause small changes to the orbital energies by induction, while those at the β-pyrrole positions more strongly conjugate into the aromatic system. In addition, however, we find evidence that β-pyrrole nitro groups distort the porphyrin, creating two non-planar conformations with distinct properties. This unexpected result helps explain the anomalous photophysics of nitro-porphyrins reported throughout the literature, including inhomogeneous line broadening and biexponential fluorescence decay.
Nitro-porphyrins are an imn class="Chemical">portant class of commercial dyes with a range of potential applications. The nitro group is known to dramatically affect the photophysics of the porphyrin, but there are few systematic investigations of the contributing factors. To address this deficiency, we present spectroscopic studies of a series of nitro-porphyrins, accompanied by density functional theory calculations to elucidate their structures. In particular, we explore how the positions of the substituents affect the energy levels and nuclear geometry. As expected, nitro groups on the meso-phenyl rings cause small changes to the orbital energies by induction, while those at the β-pyrrole positions more strongly conjugate into the aromatic system. In addition, however, we find evidence that β-pyrrolenitro groups distort the porphyrin, creating two non-planar conformations with distinct properties. This unexpected result helps explain the anomalous photophysics of nitro-porphyrins reported throughout the literature, including inhomogeneous line broadening and biexponential fluorescence decay.
Authors: Christopher Farley; N V S Dinesh K Bhupathiraju; Bianca K John; Charles Michael Drain Journal: J Phys Chem A Date: 2016-09-14 Impact factor: 2.781
Authors: D Gust; T A Moore; D K Luttrull; G R Seely; E Bittersmann; R V Bensasson; M Rougée; E J Land; F C De Schryver; M Van der Auweraer Journal: Photochem Photobiol Date: 1990-04 Impact factor: 3.421