Ruthenoarenes versus Phenol Derivatives as Axial Linkers for Subporphyrazine Dimers and Trimers

Abstract

The subporphyrazine (SubPz) dimer diboron(III) [μ-1',4'-benzenediolato][bis-(1,2,6,7,11,12-hexapropylsubporphyrazinato)] (2) and trimer triboron(III)[μ-1',3',5'-benzenetriolato][tris-(1,2,6,7,11,12-hexapropylsubporphyrazinato)] (4), consisting of SubPz units assembled through their axial positions by hydroquinone- and phloroglucinol-linkers, respectively, have been prepared. Selective ruthenium-π-coordination to the linking aromatic rings afforded SubPz arrays 8 and 9, respectively. These latter systems displayed different degrees of electronic communication between the macrocycles relative to 2 and 4 as inferred from analyses of the ground- and excited-state features. For instance, as revealed by time-resolved pump probe transient absorption spectroscopy, the excited singlet states of dimer 2 and trimer 4 undergo rather rapid deactivation. In contrast, the presence of a ruthenoarene linker, as in 8 and 9, serves to increase the SubPz singlet excited state lifetimes; these now reach values similar to those seen in the case of monomeric SubPz compounds that either do or do not contain ruthenoarene subunits (i.e., 7 and 6, respectively). These findings are ascribed to the redox active nature of the hydroquinone and phloroglucinol linkers in 2 and 4 and a change in the electronics that results from organometallic functionalization.

Synthesis of Aza-, Oxa-, and Thiaporphyrins and Related Compounds

“…Torres et al also studied the intrinsic effects of the axial and peripheral substituents on the reactivity, optical and electrochemical properties, and crystal packing characteristics of the subporphyrazine π-systems. , Notably, a reduction in the number of π electrons from 18 (porphyrazines) to 14 (subporphyrazines) led to large hypsochromic shifts in the Soret and Q bands. Alkylthio-substituted derivatives 148 exhibited two broad bands in the visible region; the first of these bands (λ max 444 nm) was assigned to n−π* transitions from the lone pair of electrons on the peripheral sulfur to the subporphyrazine π* orbital, whereas the second band (λ max 559 nm) was assigned to the Q-band of subporphyrazine.…”

Expanding the Subporphyrazine Chromophore by Conjugation of Phenylene and Vinylene Substituents: Rainbow SubPzs

“…Contrasting, studies on the properties and applications of SubPzs are very scarce, probably due to the difficulties associated with their preparation. In particular, peripheral functionalization still remains a challenge. , On the other hand, axial substitution works smoothly for both SubPzs − and SubPs, while it is an issue for SubPcs . Some examples of SubPzs bearing fused heterocycles at their periphery, namely, thiophene, pyrazine, dibenzoquinoxaline, and thiadiazole or selenadiazole, have been the object of recent reports.…”

Oxidation-Induced Detachment of Ruthenoarene Units and Oxygen Insertion in Bis-Pd(II) Hexaphyrin π-Ruthenium Complexes

“…On the other hand, triple-decker π-ruthenium complex of bis-Pd(II) [26]hexaphyrin 3 possesses two ( p -cymene)Ru II fragments sitting on the two Pd II metal centers and the inner pyrrolic β-carbon atoms in a η 6 -coordinated manner on both sides of the hexaphyrin. In the literature, π-metal complexes of porphyrinoids have been limited to those based on porphyrin, porphycene, subphthalocyanine, and subporphyrazine scaffolds [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ], and no examples had been reported for expanded porphyrin π-metal complexes before our report [ 8 ]. Interestingly, complexes 1 and 2 showed attenuated macrocyclic paratropic ring currents, probably due to the coordination-induced attenuation of the global conjugation circuit, while complex 3 showed distinct 26π aromaticity.…”