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Abstract Near‐infrared (NIR) absorbing electron donor‐acceptor (D−A) chromophores have been at the forefront of current energy research owing to their facile charge transfer (CT) characteristics, which are primitive for photovoltaic applications. Herein, we have designed and developed a new set of benzothiadiazole (BTD)‐based tetracyanobutadiene (TCBD)/dicyanoquinodimethane (DCNQ)‐embedded multimodular D−A systems (BTD1‐BTD6) and investigated their inherent photo‐electro‐chemical responses for the first time having identical and mixed terminal donors of variable donicity. Apart from poor luminescence, the appearance of broad low‐lying optical transitions extendable even in the NIR region (>1000 nm), particularly in the presence of the auxiliary acceptors, are indicative of underlying nonradiative excited state processes leading to robust intramolecular CT and subsequent charge separation (CS) processes in these D−A constructs. While electrochemical studies identify the moieties involved in these photo‐events, orbital delocalization and consequent evidence for the low‐energy CT transitions have been achieved from theoretical calculations. Finally, the spectral and temporal responses of different photoproducts are obtained from femtosecond transient absorption studies, which, coupled with spectroelectrochemical data, identify broad NIR signals as CS states of the compounds. All the systems are found to be susceptible to ultrafast (~ps) CT and CS before carrier recombination to the ground state, which is, however, significantly facilitated after incorporation of the secondary TCBD/DCNQ acceptors, leading to faster and thus efficient CT processes, particularly in polar solvents. These findings, including facile CT/CS and broad and intense panchromatic absorption over a wide window of the electromagnetic spectrum, are likely to expand the horizons of BTD‐based multimodular CT systems to revolutionize the realm of solar energy conversion and associated photonic applications. 

A zinc phthalocyanine–pyrroloperylenediimide dyad connected through a nitrogen heteroatom (PDI‐N‐ZnPc) has been newly synthesized and characterized. Solvent‐polarity‐dependent singlet–singlet energy transfer and electron‐transfer quenching were envisioned from absorption and steady‐state fluorescence studies. Electrochemical and spectroelectrochemical studies enabled the assessment of the redox potentials of the donor and acceptor entities, as well as the spectral characterization of the one‐electron oxidation and reduction products. Density functional theory (DFT) studies were performed to investigate the geometry and electronic structure, as well as the role of N‐connectivity in determining the relative orientation of the entities. Further, time‐dependent DFT studies helped establish the different excited states responsible for promoting charge separation. An energy diagram was subsequently established to visualize different photophysical events. Finally, femtosecond transient absorption spectral studies were performed in both nonpolar and polar solvents to observe energy‐ and electron‐transfer events. The kinetic data were subsequently analyzed using global and target analyses. The persistence of the charge‐separated state in the present dyad, compared with earlier reported ZnPc–PDI dyads featuring carbon–carbon connectivity, was the primary outcome of the present study, highlighting the role of heteroatom linkage in regulating electron‐transfer dynamics in donor–acceptor conjugates. 

This study presents the synthesis and electrochemical characterization of meso-tetracyanobutadiene (TCBD)-functionalized diphenylporphyrin (DPP) complexes incorporating copper (Cu) and nickel (Ni) metals. These push–pull metallo diphenylporphyrin–TCBD complexes were synthesized via a [2 + 2] cycloaddition–retroelectrocyclization reaction between 5-bromo-15-formyl-10,20-diphenylporphyrin metal(II) complexes (M = Cu, Ni) and tributyl(phenylethynyl)stannate, followed by tetracyanoethylene (TCNE) addition. The resulting TCBD-functionalized porphyrins were obtained in moderate yields (70–75%) and thoroughly characterized by 1H and 13C NMR, UV-Vis spectroscopy, MALDI-TOF-MS, and single-crystal XRD. Although the single-crystal X-ray structure of NiDPP was solved, DFT calculations were used to determine the structures of the donor–acceptor MDPP-TCBD systems and to visualize their electronic structures. HOMO on the porphyrin π system and LUMO on the TCBD entity were observed, and energy level diagrams clearly laid out the electron donor and acceptor parts of the molecular systems. As expected, these novel donor–acceptor porphyrinoid assemblies exhibited enhanced push–pull properties in both the ground and excited states. Femtosecond transient absorption studies revealed that both NiDPP-TCBD and CuDPP-TCBD populate the charge-transfer state upon photoexcitation, with lifetimes of 383.1 ps and 484.7 ps, respectively, in benzonitrile. The charge-transfer states populated the triplet or doublet states (in the case of CuDPP) before returning to the ground state. 

Novel bis-phenothiazine-C₆₀conjugates, incorporating strong electron acceptors, TCBD or DCNQ, between the two phenothiazine entities, have been newly synthesized. The involvement of C₆₀as the terminal electron acceptor is demonstrated. 

The significance of perylenediimide (PDI) in promoting excited charge transfer in push–pull systems carrying TCBD–TPA and DCNQ–TPA, is demonstrated using femtosecond transient absorption and other pertinent methods. 

A zinc phthalocyanine-pyrroloperylenediimide dyad connected through a nitrogen heteroatom (PDI-N-ZnPc) has been newly synthesized and characterized. Solvent polarity-dependent singlet-singlet energy transfer and electron transfer quenching were envisioned from absorption and steady-state fluorescence studies. Electrochemical and spectroelectrochemical studies enabled the assessment of the redox potential of the donor and acceptor entities, as well as the spectral characterization of the one-electron oxidation and reduction products. DFT studies were performed to investigate the geometry and electronic structure, as well as the role of N-connectivity in determining the relative orientation of the entities. Further, time-dependent DFT studies helped establish the different excited states responsible for promoting charge separation. An energy diagram was subsequently established to visualize different photo-physical events. Finally, femtosecond transient absorption spectral studies were performed in both nonpolar and polar solvents to observe energy and electron transfer events. The kinetic data were subsequently analyzed using global and target analyses. The persistence of the charge-separated state in the present dyad, compared with earlier reported ZnPc-PDI dyads featuring carbon-carbon connectivity, was the primary outcome of the present study, highlighting the role of heteroatom linkage in regulating electron transfer dynamics in donor-acceptor conjugates. 

The importance of diameter-sorted single-wall carbon nanotubes (SWCNTs) non-covalently bound to a donor-acceptor molecular cleft, 1, in prolonging the lifetime of charge-separated states is successfully demonstrated. For this, using a multi-step synthetic procedure, a wide-band capturing, multi-modular, C60-bisstyrylBODIPY-(zinc porphyrin)2, molecular cleft 1, was newly synthesized and shown to bind diameter sorted SWCNTs. The molecular cleft and its supramolecular assemblies were characterized by a suite of physico-chemical techniques. Free-energy calculations suggested that both the (6,5) and (7,6) SWCNTs bound to 1 act as hole acceptors during the photo-induced sequential electron transfer events. Consequently, selective excitation of 1 in 1:SWCNT hybrids revealed a two-step electron transfer leading to the formation of charge-separated states. Due to the distal separation of the cation and anion radical species within the supramolecules, improved lifetimes of the charge-separated states could be achieved. The present supramolecular strategy of improving charge separation involving SWCNTs and donor-acceptor molecular cleft highlights the potential application of these hybrid materials for various light energy harvesting and optoelectronic applications.