Ni^II tetrahydronorcorroles: antiaromatic porphyrinoids with saturated pyrrole units

Abstract

While hydrogenated porphyrins are abundant in natural and synthetic compounds, antiaromatic hydrogenated porphyrinoids have not been synthesized to date. Here, we report bacteriochlorin-like Ni(II) tetrahydronorcorrole complexes as the first examples of antiaromatic porphyrinoids that contain saturated pyrrole units.

Boron(III) Carbazosubphthalocyanines: Core‐Expanded Antiaromatic Boron(III) Subphthalocyanine Analogues

“…All these signals were slightly upfield‐shifted when compared with those for carbazoles and phthalocyanines, and could be attributed to the paratropic ring current arising from the antiaromatic core of these compounds. The effect, however, was not as large as that of the previously reported porphyrinoids based on the degree of upfield shift . The relatively large upfield shift for the two isoindole protons’ singlets for 3 a , 3 c , and 3 d could be due to the additional anisotropic shielding effect by the neighboring aryl rings.…”

“…To date, a number of antiaromatic porphyrins and their ring‐expanded, ring‐contracted (e.g. norcorroles and tetrahydronorcorroles), and core‐modified (e.g. isophlorins, oxatriphyrins, and phenanthriporphyrin) analogues have been reported.…”

Boron(III) Carbazosubphthalocyanines: Core‐Expanded Antiaromatic Boron(III) Subphthalocyanine Analogues

“…This result can explain why these protons are not substantially upfield-shifted as observed for other antiaromatic porphyrin derivatives. [5][6][7][8] Apart from 3a,w ea lso computed the 1 HNMR data for the hypothetical boron-free analogue of 3a.The signals of the two inner pyrrole protons were predicted at d = 20.47 ppm, and were substantially downfield-shifted compared with those of the hypothetical boron-free SubPc analogue [at d = 0.76 (convex site) and 5.78 ppm (concave site);see Figure S4]. The NICS(0) values in the center of the boron-free analogue of 3a and SubPc were calculated to be 8.33 and À13.5, respectively (see Figure S5).…”

“…All these signals were slightly upfield-shifted when compared with those for carbazoles and phthalocyanines,a nd could be attributed to the paratropic ring current arising from the antiaromatic core of these compounds.T he effect, however,w as not as large as that of the previously reported porphyrinoids based on the degree of upfield shift. [5][6][7][8] Ther elatively large upfield shift for the two isoindole protons singlets for 3a, 3c,and 3d could be due to the additional anisotropic shielding effect by the neighboring aryl rings.…”

“…[1] Apart from their intrinsic interest from at heoretical point of view,t hese compounds exhibit intriguing optical and electronic properties.T hey can serve as potential electrode-active materials in rechargeable batteries [2] and ambipolar semiconductors for field-effect transistors. [3] To date,an umber of antiaromatic porphyrins [4] and their ring-expanded, [5] ring-contracted (e.g.norcorroles [6] and tetrahydronorcorroles [7] ), and core-modified (e.g.i sophlorins, [1c,8] oxatriphyrins, [9] and phenanthriporphyrin [10] ) analogues have been reported. Thea romaticity of these systems can be modulated through changing the physical and chemical environments,and by photoswitching the electronic states.…”