Synthesis, Characterization, and Properties of Subporphyrazines: A New Class of Nonplanar, Aromatic Macrocycles with Absorption in the Green Region

Abstract

Novel subphthalocyanine analogues that display strong absorption in the green region have been synthesized by using a boron template cyclotrimerization of maleonitrile derivatives. The spectroscopic properties of these macrocycles indicate that, like subphthalocyanines, they have 14 pi electrons and are aromatic compounds with a conical shape. The removal of the three fused benzene rings from the subphthalocyanine skeleton produces a 75-80 nm blue shift of the Q-band and a slight lowering of the absorption coefficients for this band. In addition, the reduction of the pi system from 18 to 14 electrons that accompanies progression from porphyrazines to subporphyrazines causes a hypsochromic shift of the Q-band of around 100 nm. Subporphyrazines that are peripherally functionalized with six thioether chains, and in which the sulfur atoms are attached directly to the pyrrole moieties, exhibit optical features that may be explained in terms of the extension of pi conjugation over the six thiolene groups, as well as strong pi donation from the sulfur lone pairs to the macrocycle. These two effects are quantitatively and qualitatively very similar to those observed for porphyrazines that possess the same type of substitution. In addition, the mesomorphic behavior at low temperatures of a macrocycle that is substituted with six thiododecyl chains was demonstrated by using differential scanning calorimetry and optical polarising microscopy.

Synthesis and Switching the Aromatic Character of Oxatriphyrins(2.1.1)

“…The rational approach for the synthesis of boron(III) triphyrin(1.1.1) 1-B, [4] boron(III) subporphyrazines, [5] and boron(III) subphthalocyanines, [6] involves a templating effect. The rational approach for the synthesis of boron(III) triphyrin(1.1.1) 1-B, [4] boron(III) subporphyrazines, [5] and boron(III) subphthalocyanines, [6] involves a templating effect.…”

Photooxidation of Dithiaethyneporphyrin

“…The rise in interest was caused by reports on the synthesis of subpor-phyrins, the new, genuine contracted, aromatic 14π-electron porphyrins, [5,6] simply related to subphthalocyanines, the macrocycles widely explored because of their specific optical properties. [7] The initial, synthetic reports on subporphyrins triggered a variety of peripheral modifications of their skeleton displaying a significant influence of meso-and β-substituents on electrochemical and optical properties. [8] Interestingly, the new types of contracted porphyrinoids, imprinted into the N-fused porphyrin frame, have been obtained recently by insertion of boron(III), [9] silicon(IV), [10] or phosphorus(V) [11] into N-confused porphyrin or phosphorus(V) into 21-telluraporphyrin.…”

Phthalocyanine, Porphyrin, Cyclodextrin, and Polymer Systems Suitable for Studying by Circular Dichroism, Magnetic Circular Dichroism, and/or Electrochemistry

“…7 As a ring-contracted subPc, subtriazaporphyrin (subAzP), consisting of three pyrrole rings and three meso-nitrogen atoms, was reported for the first time by two groups. 8,9 Our subAzP 4 contained six ethyl groups, which affect the spectroscopic properties only marginally, so that we could collect properties inherent to the subAzP skeleton ³ structure. Both the Q and Soret bands appeared at significantly shorter wavelength than those of the subPcs with concomitant decrease of absorption coefficients, as has been predicted by molecular orbital (MO) calculations.…”

“…8,9 Our subAzP 4 contained six ethyl groups, which affect the spectroscopic properties only marginally, so that we could collect properties…”