Push–pull systems comprising of triphenylamine–tetracyanobutadiene (TPA‐TCBD), a high‐energy charge‐transfer species, are linked to a near‐IR sensitizer, azaBODIPY, for promoting excited‐state CS. These systems revealed panchromatic absorption owing to intramolecular CT and near‐IR absorbing azaBODIPY. Using electrochemical and computational studies, energy levels were established to visualize excited state events. Fs‐TA studies were performed to monitor excited state CT events. From target analysis, the effect of solvent polarity, number of linked CT entities, and excitation wavelength dependence in governing the lifetime of CS states was established. Electron exchange between two TPA‐TCBD entities in 3 seem to prolong lifetime of the CS state. We have been successful in demonstrating efficient CS upon both high‐energy CT and low‐energy near‐IR excitations, signifying importance of these push–pull systems for optoelectronic applications operating in the wide optical window.

The significance of electron exchange in stabilizing the charge-separated state is revealed in multi-modular donor–acceptor conjugates.

Prolonging the lifetime of charge-separated states (CSS) is of paramount importance in artificial photosynthetic donor−acceptor (DA) constructs to build the next generation of light-energy-harvesting devices. This becomes especially important when the DA constructs are closely spaced and highly interacting. In the present study, we demonstrate extending the lifetime of the CSS in highly interacting DA constructs by making use of the triplet excited state of the electron donor and with the help of excitation wavelength selectivity. To demonstrate this, π-conjugated phenothiazine sulfone-based push−pull systems, PTS2−PTS6 have been newly designed and synthesized via the Pdcatalyzed Sonogashira cross-coupling followed by [2 + 2] cycloaddition−retroelectrocyclization reactions. Modulation of the spectral and photophysical properties of phenothiazine sulfones (PTZSO 2 ) and terminal phenothiazines (PTZ) was possible by incorporating powerful electron acceptors, 1,1,4,4-tetracyanobutadiene (TCBD) and cyclohexa-2,5-diene-1,4-diylidene-expanded TCBD (exTCBD). The quadrupolar PTS2 displayed solvatochromism, aggregation-induced emission, and mechanochromic behaviors. From the energy calculations, excitation wavelength-dependent charge stabilization was envisioned in PTS2−PTS6, and the subsequent pump−probe spectroscopic studies revealed charge stabilization when the systems were excited at the locally excited peak positions, while such effect was minimal when the samples were excited at wavelengths corresponding to the CT transitions. This work reveals the impact of wavelength selectivity to induce charge separation from the triplet excited state in ultimately prolonging the lifetime of CCS in highly interacting push−pull systems.

β-Functionalized push-pull zinc opp-dibenzoporphyrins were designed and synthesized as sensitizers for dye-sensitized solar cells. The utilization of arylamine to replace aliphatic amine as the donor groups has been proved to...

Understanding the process of charge transfer in multimodular push−pull systems is of great significance for technology breakthroughs, especially in the areas of light energy conversion and building optoelectronic devices. In this study, a series of symmetrical and unsymmetrical push−pull systems, 1−4, were designed and synthesized via the Pd-catalyzed Sonogashira crosscoupling reaction, followed by the [2 + 2] cycloaddition−retroelectrocyclization reaction. The D−π−D 3 ′ and D−A n −D 3 ′ (n = 0−3) molecular configurations of 1−4 contained triphenylamine (TPA), D, as the central core and phenothiazine (PTZ), D′, as the endcapping unit as a donor and TCBD as the central electron acceptor, A. As control compounds, C1−C4 with a general formula D−A n were also synthesized to realize the effect of terminal PTZ in the charge transfer events. The photophysical properties of both star-shaped symmetrical and unsymmetrical 2−4 molecules exhibited a broad intramolecular charge transfer (ICT, also known as charge polarization) band in the visible−near-IR region due to strong push−pull interactions. The electrochemical properties of both the 1−4 and C1−C4 series exhibited multistep redox processes, and spectroelectrochemical studies helped in arriving at the spectral features of the charge transfer species. Frontier orbitals generated on DFT optimized structures helped in visualizing the charge transfer within the different donor and acceptor entities of a given push−pull system. Finally, femtosecond transient absorption spectral studies followed by data analysis by target analyses were utilized to demonstrate excited charge transfer. The terminal PTZ in compounds 2−4 is shown to stabilize the charge transfer state compared to the corresponding control compounds revealing its significance in modulating charge transfer properties.