A Structural Model of Nitro‐Porphyrin Dyes Based on Spectroscopy and Density Functional Theory

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. © 2017 Wiley Periodicals, Inc.

Syntheses, crystal structures, photo-physical properties, antioxidant and antifungal activities of Mg(II) 4,4′-bipyridine and Mg(II) pyrazine complexes of the 5,10,15,20 tetrakis(4–bromophenyl)porphyrin

“…Porphyrins and their metal complexes were considered as active materials used in polyme rization [1][2][3] and they also exhibited important function as catalysts, in medicinal and pharmaceutical fields [4][5][6], and functional dyes and pigments [7]. For example, iron and manganese porphyrinic complexes were used as efficient catalysts for hydroxylation of alkanes and epoxidation of alkenes [8][9][10][11][12][13][14].…”

Спектры РКР и механизмы тушения флуоресценции beta-нитро-тетрафенилпорфирина

“…Недавно в работе [11] на основе расчетов методом B3LYP/6-31g(d) был обнаружен ряд конформеров ТPP-NO 2 , названных конформерами промежуточного типа.…”

“…В последнем случае энергия CT-состояний оказалась заметно выше энергии флуоресцентного состояния, и авторы предположили, что это связано с неучетом в расчетах поляризующего влияния среды. В работе [11] для интерпретации структурных, спектральных и люминесцентных свойств ряда нитропрозводных TPP привлекались данные расчетов методами DFT и TDDFT. Проведенный анализ, однако, не позволил установить положение и природу СT-состояний.…”

Applications of Fluorous Porphyrinoids: An Update†

“…All of these species retain an 18 electron conjugation pathway consistent with the Hückel’s rule for aromaticity, as does phthalocyanine (Pc) with its 38 π electrons (2). The basic features of the electronic excitation and emission spectra of porphyrinoids and their metallic derivatives are well explained by Gouterman’s four‐orbital model (3), and further refinements can be done with higher‐level quantum computational methods such as DFT (4–6).…”