Electrocatalytic oxidation of pyrrole on a quasi-reversible silver nanodumbbell particle surface for supramolecular porphyrin production

Photoactive supramolecular porphyrin assemblies are attractive molecules for light-harvesting applications. This is due to their relatively non-toxicity, biological activities and charge and energy exchange characteristics. However, the extreme cost associated with their synthesis and requirements for toxic organic solvents during purification pose a challenge to the sustainability characteristics of their applications. This work presents the first report on the sustainable synthesis, spectroscopic and photophysical characterizations of a near-infrared (NIR) absorbing Ca(II)-meso-tetrakis (4-hydroxyphenyl)porphyrin using an electrolyzed pyrrole solution. The latter was obtained by cycling the pyrrole solution across the silver nanodumbbell particle surface at room temperature. The electrolyzed solution condensed readily with acidified p-hydroxybenzaldehyde, producing the targeted purple porphyrin. The non-electrolyzed pyrrole solution formed a green substance with significantly different optical properties. Remarkable differences were observed in the voltammograms of the silver nanodumbbell particles and those of the conventional gold electrode during the pyrrole cycling, suggesting different routes of porphyrin formation. The rationale behind these formations and the associated mechanisms were extensively discussed. Metalation with aqueous Ca2+ ion caused a Stokes shift of 38.75 eV. The current study shows the advantage of the electrochemical method towards obtaining sustainable light-harvesting porphyrin at room temperature without the need for high-energy-dependent conventional processes.

Donor-acceptor interactions of gold(III) porphyrins with cobalt(II) phthalocyanine: chemical structure of products, their spectral characterization and DFT study

In the context of the development of coordination energy-harvesting systems, the axial bonding of cobalt(II) octakis(3,5-di-tert-butylphenoxy)phthalocyanine (1) with gold(III) 2,3,7,8,12,18-hexamethyl,13,17-diethyl,5-(pyridin-4-yl)- and (2,3,7,8,12,18-hexamethyl,13,17-diethyl,5-(pyridin-3-yl)porphin (2 and 3), the structure, the spectral/electrochemical properties of the resulting donor-acceptor complexes and photoinduced electron transfer in them are studied. The process of the dyad formation passing as self-assembly in the donor-acceptor phthalocyanine-porphyrin systems was explored using UV-Visible, IR, and ¹H NMR spectroscopy and mass spectrometry. The geometric and electronic structures of the dyads were identified using density functional theory (DFT) and time-dependent DFT calculations. The electron transfer in the coordination complexes studied was confirmed by recording the radical ion pairs namely 1˙⁺:2˙^-/1˙⁺:3˙^- and measuring the kinetics of the photoinduction and decay of these states by a femtosecond laser photolysis technique. The effect of the gold(III) porphyrin macrocycle nature in the lifetime of radical ion pairs was shown. The redox potential values for the coordination dyads and the photoelectrochemical parameters defining their perspective in design and understanding of PET systems were observed using the cyclic voltammetry/amperometry methods and the short-circuited electrochemical cell Ti|a dyad film|0.5 M Na₂SO₄|Pt, respectively.

Applications of Photoinduced Phenomena in Supramolecularly Arranged Phthalocyanine Derivatives: A Perspective

This review focuses on the description of several examples of supramolecular assemblies of phthalocyanine derivatives differently functionalized and interfaced with diverse kinds of chemical species for photo-induced phenomena applications. In fact, the role of different substituents was investigated in order to tune peculiar aggregates formation as well as, with the same aim, the possibility to interface these derivatives with other molecular species, as electron donor and acceptor, carbon allotropes, cyclodextrins, protein cages, drugs. Phthalocyanine photo-physical features are indeed really interesting and appealing but need to be preserved and optimized. Here, we highlight that the supramolecular approach is a versatile method to build up very complex and functional architectures. Further, the possibility to minimize the organization energy and to facilitate the spontaneous assembly of the molecules, in numerous examples, has been demonstrated to be more useful and performing than the covalent approach.

Assemblies of Boron Dipyrromethene/Porphyrin, Phthalocyanine, and C60 Moieties as Artificial Models of Photosynthesis: Synthesis, Supramolecular Interactions, and Photophysical Studies

A series of light-harvesting conjugates based on a zinc(II) phthalocyanine core with either two or four boron dipyrromethene (BODIPY) or porphyrin units have been synthesized and characterized. The conjugation of BODIPY/porphyrin units can extend the absorptions of the phthalocyanine core to cover most of the visible region. Upon addition of an imidazole-substituted C₆₀ (C₆₀ Im), it can axially bind to the zinc(II) center of the phthalocyanine core through metal-ligand interactions. The resulting complexes form photosynthetic antenna-reaction center mimics in which the BODIPY/porphyrin units serve as the antennas to capture the light and transfer the energy to the phthalocyanine core by efficient excitation energy transfer. The excited phthalocyanine is then quenched by the axially bound C₆₀ Im moiety by electron transfer, which has been supported by computational studies. The photoinduced processes of the assemblies have been studied in detail by various steady-state and time-resolved spectroscopic methods. By femtosecond transient absorption spectroscopic studies, the lifetimes of the charge-separated state of the bis(BODIPY) and bis(porphyrin) systems have been determined to be 3.2 and 4.0 ns, respectively.

Probing the in-air growth of large area of 3D functional structures into a 2D supramolecular nanoporous network

2D host–guest chemistry combined with drop-casting allows to trap functionalized 3D Zn–phthalocyanine complex into a large 2D porous supramolecular template.

Axially substituted phosphorous(v) corrole with polycyclic aromatic hydrocarbons: syntheses, X-ray structures, and photoinduced energy and electron transfer studies

Excited state energy and electron transfer processes in naphthalene and pyrene appended phosphorous(v) corroles.

Synthesis and comparative charge transfer studies in porphyrin–fullerene dyads: mode of attachment effect

Two types of dyads having different modes of attachment i.e. cyclopropanation vs. pyrrolidine type in porphyrin–fullerene linked systems are compared for their photophysical properties. Dyad II with pyrrolidine type of linkage shows faster charge separation and generation of long lived charge separated states. It also shows a new property of thermally activated electrical conductivity which makes it potential candidate for organic electronic devices.