Synthesis and Properties of Covalently Linked Trichromophore Systems

Azophenine as Central Core for Efficient Light Harvesting Devices

The notoriously non-luminescent uncycled azophenine (Q) was harnessed with Bodipy and zinc(II)porphyrin antennas to probe its fluorescence properties, its ability to act as a singlet excited state energy acceptor and to mediate the transfer. Two near-IR emissions are depicted from time-resolved fluorescence spectroscopy, which are most likely due to the presence of tautomers of very similar calculated total energies (350 cm^-1 ; DFT; B3LYP). The rates for energy transfer, k_ET (S₁ ), for ¹ Bodipy*→Q are in the order of 10¹⁰ -10¹¹  s^-1 and are surprisingly fast when considering the low absorptivity properties of the lowest energy charge transfer excited state of azophenine. The rational is provided by the calculated frontier molecular orbitals (MOs) which show atomic contributions in the C₆ H₄ C≡CC₆ H₄ arms, thus favoring the double electron exchange mechanism. In the mixed-antenna Bodipy-porphyrin star molecule, the rate for ¹ Bodipy*→porphyrin has also been evaluated (≈16×10¹⁰  s^-1 ) and is among the fastest rates reported for Bodipy-zinc(II)porphyrin pairs. This astonishing result is again explained from the atomic contributions of the C₆ H₄ C≡CC₆ H₄ and C≡CC₆ H₄ arms thus favouring the Dexter process. Here, for the first time, this process is found to be sensitively temperature-dependent. The azophenine turns out to be excellent for electronic communication.

Stable meso-Fluorenyl Smaragdyrin Monoradical

The facile synthesis and physical characterization of a meso-fluorenyl smaragdyrin monoradical 4, which is stable due to efficient spin delocalization and kinetic blocking, is reported. It has a small energy gap and can be oxidized and reduced into the respective cation and anion, showing different charge distribution and electronic absorption properties.

meso-2′-Linked porphyrin–BODIPY hybrids: synthesis and efficient excitation energy transfer

Three meso-2′-linked porphyrin–BODIPY hybrids (BDP–ZnP, 2BDP–ZnP, and 4BDP–ZnP) were synthesized, and fast and highly efficient energy transfer was achieved.

Synthesis and properties of rhenium(I) bridged boron-dipyrromethene dyad

We synthesized the hexa-coordinated Re ( I ) bridged BODIPY dyad 1 in decent yield by thermal reaction of benzimidazole substituted BODIPY 2 with Re ( CO )5 Cl . The dyad 1 was characterized by 1 H , 13 C , 11 B , 19 F NMR, ESI-MS, FTIR, UV-vis, and electrochemical techniques. In Re ( I ) bridged dyad 1, the Re ( I ) ion is hexa-coordinated and coordinates with nitrogen atoms of two benzimidazole units, three axial carbonyl ligands and one chloride atom. The presence of three carbonyl groups in dyad 1 was verified by 13 C NMR and IR spectroscopy. The absorption and steady-state fluorescence spectra of Re ( I ) bridged BODIPY dyad showed a slightly broad and hypsochromically shifted absorption and emission bands compared to BODIPY 2. The electrochemical studies indicated that, the Re ( I ) bridge BODIPY dyad 1 was easy to reduce compared to BODIPY 2 supporting the electron deficient nature dyad upon Re ( I ) ion binding. The molecular structure of dyad 1 was further elucidated by DFT computational studies.

Design, synthesis and photophysical studies of dipyrromethene-based materials: insights into their applications in organic photovoltaic devices

This review article presents the most recent developments in the use of materials based on dipyrromethene (DPM) and azadipyrromethenes (ADPM) for organic photovoltaic (OPV) applications. These chromophores and their corresponding BF2-chelated derivatives BODIPY and aza-BODIPY, respectively, are well known for fluorescence-based applications but are relatively new in the field of photovoltaic research. This review examines the variety of relevant designs, synthetic methodologies and photophysical studies related to materials that incorporate these porphyrinoid-related dyes in their architecture. The main idea is to inspire readers to explore new avenues in the design of next generation small-molecule and bulk-heterojunction solar cell (BHJSC) OPV materials based on DPM chromophores. The main concepts are briefly explained, along with the main challenges that are to be resolved in order to take full advantage of solar energy.

Antenna effects in truxene-bridged BODIPY triarylzinc(ii)porphyrin dyads: evidence for a dual Dexter–Förster mechanism

BODIPY uses the truxene bridge to transfer its S₁ energy to the zinc(ii)porphyrin acceptors via a Dexter mechanism almost exclusively.

Smaragdyrins: emeralds of expanded porphyrin family

Porphyrins are tetrapyrrolic 18 π electron conjugated macrocycles with wide applications that range from materials to medicine. Expanded porphyrins, synthetic analogues of porphyrins that contain more than 18 π electrons in the conjugated pathway, have an increased number of pyrroles or other heterocyles or multiple meso-carbon bridges. The expanded porphyrins have attracted tremendous attention because of unique features such as anion binding or transport that are not present in porphyrins. Expanded porphyrins exhibit wide applications that include their use in the coordination of large metal ions, as contrasting agents in magnetic resonance imaging (MRI), as sensitizers for photodynamic therapy (PDT) and as materials for nonlinear optical (NLO) studies. Pentaphyrin 1, sapphyrin 2, and smaragdyrin 3 are expanded porphyrins that include five pyrroles or heterocyclic rings. They differ from each other in the number of bridging carbons and direct bonds that connect the five heterocyclic rings. Sapphyrins were the first stable expanded porphyrins reported in the literature and remain one of the most extensively studied macrocycles. The strategies used to synthesize sapphyrins are well established, and these macrocycles are versatile anion binding agents. They possess rich porphyrin-like coordination chemistry and have been used in diverse applications. This Account reviews developments in smaragdyrin chemistry. Although smaragdyrins were discovered at the same time as sapphyrins, the chemistry of smaragdyrins remained underdeveloped because of synthetic difficulties and their comparative instability. Earlier efforts resulted in the isolation of stable β-substituted smaragdyrins and meso-aryl isosmaragdyrins. Recently, researchers have synthesized stable meso-aryl smaragdyrins by [3 + 2] oxidative coupling reactions. These results have stimulated renewed research interest in the exploration of these compounds for anion and cation binding, energy transfer, fluorescent sensors, and their NLO properties. Recently reported results on smaragdyrin macrocycles have set the stage for further synthetic studies to produce stable meso-aryl smaragdyrins with different inner cores to study their properties and potential for various applications.