meso‐Thiaporphyrinoids Revisited: Missing of Sulfur by Small Metals

Abstract

Facile synthesis of meso-aryl-substituted 5,15-dithiaporphyrins and 10-thiacorroles has been achieved by sulfidation of α,α'-dichlorodipyrrin metal complexes with sodium sulfide in DMF. Thiacorrole metal complexes exhibit distinct aromaticity due to 18 π-conjugation including the lone pair on sulfur, whereas dithiaporphyrins are nonaromatic judging from (1)H NMR spectra, X-ray analysis, and absorption spectra. We have found that Ni(II) and Al(III) dithiaporphyrin complexes undergo smooth thermal sulfur extrusion reaction to give the corresponding thiacorrole complexes, whereas free base, Zn(II), Pd(II), and Pt(II) dithiaporphyrin complexes did not exhibit the similar reactivity. The DFT calculations have elucidated a reaction pathway involving an episulfide intermediate, which can explain the markedly different reactivity among dithiaporphyrin metal complexes.

Rational Synthesis of Antiaromatic 5,15‐Dioxaporphyrin and Oxidation into β,β‐Linked Dimers

“…In addition, this kind of approach towards antiaromatic systems based on modification of main-group elements at the meso-positions is practically important although an umber of stable antiaromatic molecules have successfully been created by utilizing porphyrinoid p-conjugated systems like isophlorin, [11][12][13][14][15][16][17][18] norcorrole, [19][20][21] and expanded porphyrins. [22,23] We report, herein, the first rational synthesis of 5,15dioxaporphyrin by an ucleophilic substitution reaction of anickel bis(dipyrrin) complex with benzaldoxime followed by an annulation reaction of the a-hydroxy-substituted intermediate.Inclear contrast to the nonaromaticity of its higher congener,5 ,15-dithiaporphyrin, [7,8] 5,15-dioxaporphyrin exhibited unequivocal antiaromatic characteristics,s uch as aparatropic ring current effect and abroad absorption in the visible and near-infrared (Vis/NIR) regions,r eflecting af orbidden HOMO-LUMO transition of an intrashell nature. Thecurrent-density calculations based on the gauge-including magnetically induced current (GIMIC) method [24] also provided quantitative information about the current pathway and the net paratropic ring current of À10.9 nA/T.…”

“…The origin of these different colors lies in the removal of degeneracyo ft he HOMO by substitution of the mesocarbon atoms by more electronegative nitrogen atoms,which causes intensification of the Q-band absorption of phthalocyanine in the red region as aresult of the smaller configurational interactions of transitions between the four frontier orbitals. [6] In addition to the perturbation of the 18p-electron conjugated system, heteroatom substitution can also change the number of p-electrons involved in the main conjugation pathway.I ti s, therefore,c onceivable that in the case of modification with two chalcogen atoms,l one-pair electrons can be included to provide antiaromatic 20p-electron conjugated systems.D espite this expectation, such antiaromatic di-chalcogen-substituted porphyrin analogues have not yet been realized:5,15-dithiaporphyrin was synthesized by Johnson et al in 1970, [7] and more recently by Shinokubo et al, [8] and it is nonaromatic,w hereas 5,15-dioxaporphyrin has not been synthesized. Shinokubo et al ascribed the nonaromaticity of 5,15-dithiaporphyrin to its gable structure caused by the long CÀSb onds,w hich hindered effective overlap of p-orbitals.V ery recently,t he groups of Matano and Shinokubo independently reported the 20p-antiaromatic 5,15diaza-5,15-dihydroporphyrin.…”

Synthesis and properties of redox‐switchable zinc complexes of 10,15,20‐triaryl‐15‐aza‐5‐oxaporphyrin

“…In addition to diazaporphyrin derivatives, 20π porphyrins modified with chalcogen atoms at the 5 and 15 positions have received considerable attention from both porphyrin and heteroatom chemists . Recently, Shimizu et al .…”

“…Recently, Shimizu et al . and Shinokubo et al . independently reported the nickel(II) complex of 10,20‐diaryl‐5,15‐dioxaporphyrin (DOP) and several metal complexes and the free base of 10,20‐diaryl‐5,15‐dithiaporphyrin (DTP), respectively (Chart ).…”

Covalent Porphyrin Hybrids Linked with Dipyrrin, Bidipyrrin or Thiacorrole

“…Furthermore, when porphyrin and dipyrrin or bidipyrrin are covalently linked, the new dyes simultaneously show the rigid and planar properties of porphyrin unit and the coordination and flexible properties of the dipyrrin or bidipyrrin unit [ 42 , 43 ]. On the other hand, apart from the above-mentioned hybrids, thiacorrole [ 44 ], a meso -modified porphyrin analogue with heteroatom directly on the π-conjugation circuit, could potentially be introduced into the porphyrin hybrids; this hybrid remains unexplored. The new hybrids could possibly present interesting coordination or magnetism properties related to different units.…”