Re(I) bridged porphyrin dyads, triads and tetrads

Abstract

Porphyrin rings containing two meso-pyridyl groups either in cis or trans fashion can be used to construct Re(I) bridged multiporphyrin assemblies. The cis-dipyridyl porphyrins with various porphyrin cores such as N 4 , N 3 O, N 3 S, N 2 S 2 have been used to react with Re(CO) 5 Cl in THF at refluxing temperature and constructed planar Re(I) bridged porphyrin dyads containing either one type of porphyrin subunit or two types of porphyrin subunits. The trans-dipyridyl porphyrins have been used to construct Re(I) bridged porphyrin squares. The porphyrin dyads have been explored for singlet-singlet energy transfer studies and porphyrin squares have been used for catalysis, chemical sensing, molecular sieving and photocurrent production studies. An overview of synthesis of Re(I) bridged porphyrin dyads, triads and tetrads and their interesting photophysical properties are highlighted in this paper.

Rhenium(I)-Based Monocyclic and Bicyclic Phosphine Oxide-Coordinated Supramolecular Complexes

“…Designing supramolecular coordination complexes (SCCs), using various preprogrammed metal-based acceptors and organic-donor frameworks, has gained considerable research interest in the past two decades because of their potential applications in various fields including host–guest encapsulation, catalysis, and medicine. − Among the available metal-directed approaches, the fac- Re­(CO) 3 -core-based method is one of the well-known processes for synthesizing heteroleptic SCCs with various sizes, shapes, and functionalities. − Owing to their high significance in several important areas, research is being channeled toward synthesizing new SCCs with improved properties and designing a one-step synthetic approach for multicomponent assembly. In this direction, ditopic phosphine oxide donors have been recently introduced in place of neutral ditopic nitrogen donors, which are one of the few organic-framework-building units in heteroleptic rhenium­(I)-based SCCs .…”

Rhenium‐Carbonyl‐Based Supramolecular Coordination Complexes: Synthesis, Structure and Properties

“…The dinuclear metallacycles display fluorescence with reduced quantum yields as compared to the free porphyrin ligands owing to the presence of heavy metal ions Re(I) which enhances the chance of the intersystem crossing and reduces emission. [71] On excitation of this dyad at the excitation wavelength of N 3 O porphyrin, majority of the emission was observed for the N 3 S porphyrin unit suggesting the intramolecular energy transfer from N 3 O to N 3 S porphyrin units. The emission lifetime was estimated to be 1.38 ns observed mainly from the N 3 S porphyrin unit.…”

“…Aiming to upgrade the EnT properties of these systems, Ravikanth and coworkers introduced the core modified porphyrins where one or more pyrrolic nitrogen/s is replaced with heteroatoms (O, S, Se, Te) and synthesized a series of similar kind of porphyrin dyads. The dinuclear metallacycles display fluorescence with reduced quantum yields as compared to the free porphyrin ligands owing to the presence of heavy metal ions Re(I) which enhances the chance of the intersystem crossing and reduces emission . On excitation of this dyad at the excitation wavelength of N 3 O porphyrin, majority of the emission was observed for the N 3 S porphyrin unit suggesting the intramolecular energy transfer from N 3 O to N 3 S porphyrin units.…”

Non-Covalently Linked Multiporphyrin Arrays by Metal Coordination

“…Due to the presence of porphyrins of two different cores, the possibility of energy transfer were further studied in these dyads. His group further expanded the possibilities of metal coordinated assembly of porphyrins by the synthesis of a tryad 21 [23] (Fig. 20) where a normal N 2 S 2 porphyrin is linked covalently An elegant utilization of the complementarity between pyridyl groups of porphyrins and metalloporphyrins is established by the assembly of double stranded oligomeric porphyrin array 22 (Fig.…”

“…Tachibana et al [25] synthesized a covalently linked square shaped cyclic Zn-porphyrin dimer connected by alkynyl fluorene moieties and used it as a host to bind a RuTPP (DABCO)2 molecule, in the cavity of the cyclic dimer to construct a face to face porphyrin array [23]. The stability of the tryad is mainly due to the host-guest interaction and through steady state fluorescence and transient absorption spectroscopy an effective photoinduced electron transfer from Zn-porphyrin to Ru-porphyrin is clearly established.…”