Synthesis and Properties of Dibenzothiophene Embedded Heteroporphyrins

Abstract

A series of new stable dibenzothiophene embedded heteroporphyrins were synthesized in 6–7% yields by condensing 1 equiv of dibenzothiophene-based tripyrrane with 1 equiv of four different diols, 2,5-bis(hydroxymethyl)­heterocycles (furan, thiophene, selenophene, and tellurophene), under mild acid-catalyzed conditions in CH2Cl2. The formation of dibenzothiophene embedded heteroporphyrins was confirmed by high-resolution mass spectrometry and thoroughly characterized by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, absorption, electrochemical, and density functional theory/time-dependent density functional theory (DFT/TD-DFT) studies. The NMR studies indicated that the macrocycles were nonaromatic in nature. The electronic properties of the macrocycles were significantly altered as the heterocycle of the macrocycles was varied from furan to thiophene, selenophene, and tellurophene, as reflected clearly in the spectral and electrochemical properties. The macrocycles exhibited a sharp band in the region of 420–440 nm and a relatively broad absorption band(s) in the higher wavelength region of 550–800 nm. The oxa analogue was considerably blue-shifted as compared to the other macrocycles, whereas the tellura analogue exhibited relatively broadened and red-shifted absorption bands. Upon protonation of these macrocycles, the resulting diprotonated species displayed bathochromically shifted absorption bands, which were extended to the NIR region. DFT studies revealed that the macrocycles were highly distorted and strained and exhibited half chair conformation with restricted π-conjugation and confirmed their nonaromatic nature due to the lack of planarity of the macrocycle. TD-DFT studies were in agreement with the experimental spectral and electrochemical results.

Synthesis and Studies of Dibenzofuran Embedded Bis‐(Calix)‐Pentaphyrins

“…[11][12][13][14][15] In recent times, polyaromatic hydrocarbons/heterocycles (PAHs) were used in place of one or more pyrrole rings of porphyrinoids to generate a new type of polyaromatic embedded porphyrinoids with interesting electronic and coordination properties. [16,17] A perusal of literature revealed that the polyaromatic hydrocarbons/heterocycles such as biphenyl, [18] naphthalene, [19] phenanthrene, [20] fluorene [21,22] bipyridine, [23] phenanthroline, [24] dibenzofuran, [25] dibenzothiophene, [26] and phenothiazine [27] are few such polyaromatic hydrocarbons/heterocycles which have been introduced in place of one or more pyrrole rings of porphyrinoid framework and generated a wide range of very novel PAH embedded porphyrinoids. We used few of these PAH units such as dibenzofuran, dibenzothiophene, benzofuran, benzothiophene, fluorene and phenothiazine and synthesized very novel PAH embedded porphyrinoids which showed unique and interesting electronic and coordination properties.…”

Vacatadithiasapphyrins: Synthesis, Structure, and Spectral and Redox Properties

“…In recent times, we have reported some examples of tellurophene-containing porphyrinoids and among these, the [22]­telluradithiasapphyrins 10­(a–d) exhibit more interesting structural and electronic properties. − We thought of synthesizing [22]­vacatadithiasapphyrins by extrusion of Te from [22]­telluradithiasapphyrins 10­(a–d) since these macrocycles 10­(a–d) are aromatic and showed very interesting structural, spectral, and redox properties and anticipated that such novel properties would be retained in [22]­vacatadithiasapphyrins (Chart ). Our attempts were successful in achieving stable aromatic vacatadithiasapphyrins.…”

Two-photon absorption of 28-hetero-2,7-naphthiporphyrins: expanded carbaporphyrinoid macrocycles

“…2 In this respect, the carbaporphyrinoids embedding polycyclic aromatic hydrocarbon (PAH) subunits, namely aceneporphyrinoids, were found to be particularly intriguing, as it was demonstrated that the PAH motif is a crucial factor dictating the overall properties of the hybrid molecule. [3][4][5] The extent to which the electronic properties are altered depends on the nature of the PAH moiety present and whether it takes part in the p-delocalization with the rest of the macrocycle. In recent years aceneporphyrinoids have received a lot of attention due to their atypical p-conjugation, 6,7 their aromaticity varying from nonaromatic to antiaromatic, 8,9 and their ability to form stable organometallic complexes with metals of uncommon oxidation states.…”

“…In most cases, the modication signicantly affects the electronic properties of the molecule, which in turn changes the spectral, structural, and coordination properties. 3,5,27 In a previous study, a new constitutional isomer of naphthiporphyrin was designed and synthesized, namely 28-hetero-2,7-naphthiporphyrin. 28 The compound was proven to act as a macrocyclic ligand, as demonstrated by the formation of organophosphorus(V) complexes.…”

“…In most cases, the modification significantly affects the electronic properties of the molecule, which in turn changes the spectral, structural, and coordination properties. 3,5,27…”