Naphthylbipyrrole-Containing Amethyrin Analogue: A New Ligand for the Uranyl (UO₂²⁺) Cation

Abstract

Using naphthobipyrrole as a functional building block, a new expanded porphyrin, naphthoisoamethyrin, was prepared in 85% yield under acid-catalyzed [4 + 2] MacDonald coupling conditions. Treatment of naphthoisoamethyrin with the nonaqueous uranyl silylamide salt [UO[N(SiMe)]·2THF] yielded the corresponding uranyl complex. Upon metalation, naphthoisoamethyrin undergoes a two-electron oxidation to yield a formal 22 π-electron aromatic species, as inferred from H NMR and UV-vis spectroscopy, as well as cyclic voltammetry.

UO22+-mediated ring contraction of pyrihexaphyrin: synthesis of a contracted expanded porphyrin-uranyl complex

“…Downfield shifts in the proton resonances corresponding to the pyridine C H peaks and meso -C H peak were also seen. These shifts mirror what had been observed in the case of napthoisoamethyrin,47 isoamethyrin,48 and amethyrin40 upon uranyl coordination, findings that were attributed to formation of a globally aromatic core 49. UV-vis spectroscopic analyses revealed marked differences in comparison to previous hexaphyrin systems, as well as to the parent ligand 1 .…”

“…The resultant exo -carbaldehyde porphycenes displayed aromatic features and thus had no thermodynamic driving force to excise the pendant aldehyde 38a,c. Furthermore, uranyl (UO 2 2+ )-mediated oxidation to furnish globally aromatic expanded porphyrins has been observed with amethyrin,40 naphthoisoamethyrin,46 isoamethyrin,47 cyclo[6]pyrrole,60 and cyclo[1]furan[1]pyridine[4]pyrrole 61 , ‡‡No ring contraction or other structural modifications were observed in these instances. However, no intermediate species or postulated mechanisms have been reported for any of these systems.…”

Synthesis and Characterization of a Binuclear Copper(II) Naphthoisoamethyrin Complex Displaying Weak Antiferromagnetic Coupling

“…This has allowed new electronic pathways to be stabilized within conjugated systems and has typically led to a bathochromic shift in the corresponding absorption profiles. − The attendant rigidification might also allow the metalation chemistry to be better controlled . With such general considerations in mind, we were keen to explore whether the naphthylbipyrrole expanded porphyrin, known as naphthoisoamethyrin ( 1 ), would support the formation of binuclear metal-ion species. Here, we report the synthesis and characterization of the dicopper­(II) naphthoisoamethyrin complex.…”

Spectroscopic Study of the Salicyladazine Derivative–UO22+ Complex and Its Immobilization to Mesoporous Silica

“…Binding between UO 2 2+ and specific ligands, such as cyclic peptides [17,18], porphyrins [19,20], and naphthobipyrrole [21,22], is well known. We prepared a salicyladazine derivative as a ligand for UO 2 2+ .…”