Synthesis and Studies of Core-Modified Tellura Dithiasapphyrins

Abstract

Four different aromatic meso-substituted tellurophene-containing dithiasapphyrins were synthesized by acid-catalyzed [3+2] condensation of 16-telluratripyrrane with bithiophene diol in 22–23% yields. The structural, spectral, and electrochemical properties of tellura dithiasapphyrins were studied and compared with those of previously reported aza (pyrrole)- and other heterocycle (furan, thiophene, and selenophene)-containing dithiasapphyrins. Nuclear magnetic resonance studies indicated that the tellurophene ring in tellura dithiasapphyrins is in the normal conformation, facing toward the inner core, but flips in diprotonated derivatives to an inverted conformation, facing away from the macrocyclic core, unlike aza- and other heterocycle-containing dithiasapphyrins in which pyrrole and the corresponding heterocycle ring always prefer to be in inverted conformation in their neutral and protonated forms. The crystal structure obtained for one of the tellura dithiasapphyrins showed that the macrocycle is highly planar and the tellurophene ring is in the normal conformation. The absorption spectra of tellura dithiasapphyrins exhibited slight hypsochromic shifts compared to those of pyrrole- and other heterocycle-containing dithiasapphyrins. The redox studies indicated that the tellura dithiasapphyrins are electron deficient and readily undergoes reductions. Density functional theory and nuclear independent chemical shift studies indicated that the macrocycles are aromatic, and the computational results closely matched the experimental observations.

Vacatadithiasapphyrins: Synthesis, Structure, and Spectral and Redox Properties

“…The synthesis of vacatadithiasapphyrins 11–14 from meso -tetraaryl telluradithiasapphyrins 10a–10d is presented in Scheme . The appropriate telluradithiasapphyrins 10a–10d were treated with excess HCl in 1,2-dichlorobenzene at 180 °C for 1.5 h.…”

“…The known precursor compounds 10(a−d) were synthesized by following the reported procedures. 10 All the chemicals used for the synthesis were of reagent grade unless otherwise specified. Reaction-grade HCl obtained from Sigma-Aldrich was used as such.…”

“…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.…”

Synthesis and Studies of Mono‐functionalized Telluradithiasapphyrins and Covalently Linked Porphyrin‐ Telluradithiasapphyrin Dyads

“…Tellurophene containing porphyrinoids which resulted by replacing one or more pyrrole ring(s) of porphyrinoids are unique and quite different in terms of structure, reactivity, and coordination chemistry from other chalcogenide substituted porphyrinoids. [1][2][3][4][5][6][7] This is attributed to the large size of the tellurium atom and because of this, the distance between tellurium atom and the atom situated trans to it inside porphyrinoid core reduced. This in turn resulted in interaction between atoms inside porphyrinoid core and consequently the properties of telluraporphyrinoids are significantly altered.…”

Tuning of Heterocyclic Ring in Para-Benzi Heterosapphyrins

“…In the next step, the monocarbinol 7 was treated with 1.1 equiv of n -BuLi followed by the addition of 1.2 equiv of 4-methyl benzaldehyde or 4-methoxy benzaldehyde in dry THF at 0 °C to afford the corresponding diols 8a / 8b as white solids in 71–75% yields. The other required precursors, 16-thiatripyrrane 9 and 16-telluratripyrrane 10 were prepared by following the reported procedures. − …”