Figure‐eight Octaphyrin Bis‐Ge(IV) Complexes: Synthesis, Structures, Aromaticity, and Chiroptical Properties

Abstract

Highly twisted structures of expanded porphyrin provide a prominent basis to unravel the relationship between aromaticity and chirality. Here we report the synthesis of bis-Ge(IV) complexes of [38]octaphyrin that display rigid figure-eight structures. Two bis-Ge(IV) [38] octaphyrin isomers with respect to the stereochemistry of the axial hydroxy groups on the germanium ions were obtained and found to be aromatic. Upon oxidation with MnO 2 , these [38]octaphyrin complexes were converted to a single syntype isomer of [36]octaphyrin with retained figure-eight conformation. The enantiomers have been successfully separated by HPLC equipped with a chiral stationary phase. While aromatic [38]octaphyrin Ge(IV) complexes showed quite large molar circular dichroism of up to Δɛ = 1500 M À 1 cm À 1 with a dissymmetry factor g abs of 0.035, weakly antiaromatic [36] octaphyrin Ge(IV) complexes underscored moderate values; Δɛ = 540 M À 1 cm À 1 with g abs of 0.023. Thus, the figure-eight octaphyrin scaffold has been proved to be an attractive platform for novel chiroptical materials with tunable aromaticity.

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

“…On the other hand, the dipyrroethene, Z-1,2-di(1H-pyrrol-2yl)-1,2-di-p-tolylethene was treated with appropriate aromatic acid chloride under Grignard reaction conditions to afford compounds 9-10 in good yields. [29][30][31] The compounds 5-10 were thoroughly characterized by HR-MS, 1 H NMR and 13 C NMR spectroscopic technique. In the next step, the appropriate compound 9-10 was reduced independently to corresponding diol 11-12 by NaBH 4 in THF/CH 3 OH solution.…”

“…[9][10] Several types of core-modified porphyrinoids have been synthesized, explored their physico-chemical and coordination properties and exploited their use for wide range of applications. [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.…”

Di‐2,7‐pyrenidecaphyrin(1.1.0.0.0.1.1.0.0.0) and Its Bis‐Organopalladium Complexes: Synthesis and Chiroptical Properties

“…Five years later, Vogel and collaborators [11] introduced a strategy for locking such labile porphyrinoids that involved bis‐palladium coordination, a strategy [12] that has served as a robust paradigm for the resolution of racemic expanded porphyrinoids [13] . While this method has allowed for the successful chiral separation of octaphyrin [11, 12a–d] and hexaphyrin, [12e–f] it is important to recognize that it has yet to be generalized to include other intrinsically labile stereo‐structures [14] . On the other hand it is important to note that Latos‐Grażyński and co‐workers elegantly exploited phenanthrene to create polyaromatic hydrocarbon (PAH) embedded expanded carbaporphyrinoids.…”

Synthesis and Structural Properties of NIR‐Absorbing Pyridine‐Containing Heptaphyrins

“…[7][8][9][10] Expanded porphyrinoids are important in understanding the aromatic/anti-aromatic/nonaromatic nature of conjugated macrocycles, which depends on the number of π-electrons, nature and number of links bridging the heterocyclic units. [2,3,[10][11][12][13][14][15] The complexing ability to trap lanthanide metals make these expanded porphyrinoids a potent candidates for contrast agents in magnetic resonance imaging (MRI). [12] The photosensitizing ability to convert triplet oxygen to highly reactive and toxic singlet oxygen makes these macrocycles very important in the field of photodynamic therapy (PDT) of cancer.…”