Synthesis and Spectroelectrochemistry of N-Cobaltacarborane Porphyrin Conjugates

Abstract

N-Substituted porphyrins are well known for the distortion they exhibit of the porphyrin plane through the sp3 hybridization of one of the pyrrolenic units. They have served as model compounds in investigations of many biochemical processes. In this paper, we developed an efficient route to N-substituted porphyrins, and report the synthesis of a series of new N-substituted cobaltacarborane-porphyrins containing one or two cobaltabisdicarbollide anions linked by (CH2CH2O)2 chains to either the core porphyrin nitrogens or to a meso-aminophenyl group. These conjugates show different degrees of distortion of the porphyrin macrocycle, which affect their spectroscopic and electrochemical properties. In particular, the core N-substituted conjugates show significant fluorescence quenching in comparison with the non-core substituted macrocycles. The X-ray structures of two targeted core N-cobaltacarborane porphyrin conjugates are presented. The electrochemical and spectroelectrochemical properties of these porphyrin conjugates were investigated; while the peripheral N-substituted cobaltacarboranylporphyrins undergo three reversible reductions and three reversible oxidations (two attributed to the porphyrin and one to the CoIII cluster), the core N-substituted porphyrins exhibit complicated electrochemical behavior with coupled chemical reactions.

Polythiophenes Containing In-Chain Cobaltabisdicarbollide Centers

“…It is obvious that the second system can not be assigned to the reduction of Co(II) to Co(I), as this process is observed at much more negative potentials, below −2.0 V vs SCE. Moreover, the Co(III)/Co(II) process of the unsubstituted cobaltabisdicarbollide is characterized by a single reversible wave at E °′= −1.34 V vs SCE (8, 51). In the case of our study, the presence of two closely spaced systems is directly connected to the presence of the 2-oligothienyl substituents.…”

Boron‐Containing Lipids and Liposomes: New Conjugates of Cholesterol with Polyhedral Boron Hydrides

“…It should be noted that the parentc obalt bis(dicarbollide) andi ts derivatives demonstrate amphiphilic behavior and are able to self-association and micellization in solution. [63] The ring-opening of the 1,4-dioxane derivativeo fc obalt bis-(dicarbollide) with amines hasb een used earlier for synthesis of various biologically active boron containingm olecules including amino acids, [64] synthetic [65] and natural [66] porphyrins, etc. In this study we found that the 1,4-dioxane derivative of cobaltb is(dicarbollide)…”

Reversibly Switchable Fluorescent Molecular Systems Based on Metallacarborane–Perylenediimide Conjugates

“…Mainly, we [19] and others [20] have reported the synthesis of several conjugates of COSAN derivatives with organic fluorescent dyes (e.g. porphyrin, [20a–c] phtalocyanine, [20d, e] fluorescein, [20f] BODIPY [19b] ), essentially aiming to improve their solubility, cellular uptake and intracellular boron release for theranostic applications that combine fluorescence diagnosis with anticancer boron neutron capture therapy. In none of these cases, however, the photoluminescence properties of the fluorophores benefited from the presence of nearby metallacarborane clusters, which mainly cause a decrease of the fluorescence efficiency, [19, 20] and, to the best of our knowledge, no externally‐controlled switchable fluorescence behaviour was described for any of them.…”