Exfoliated semiconducting MoS and WS were covalently functionalized with 1,2-dithiolane-modified carbon nanodots (CNDs). The newly synthesized CND-MoS and CND-WS hybrids were characterized by spectroscopic, thermal, and electron microscopy imaging methods. Based on electronic absorption and fluorescence emission spectroscopy, modulation of the optoelectronic properties of TMDs by interfacing with CNDs was accomplished. Electrochemical studies revealed facile oxidation of MoS over WS in the examined hybrids, suggesting it to be better electron donor. Excited state events, investigated by femtosecond transient absorption spectroscopic studies, revealed ultrafast energy transfer from photoexcited CNDs to both MoS and WS. Interestingly, upon MoS photoexcitation, charge transfer from an exciton dissociation path of MoS to CNDs, within CND-MoS, was observed. However, such a process in CND-WS was found to be absent due to energetic reasons. The present study highlights the importance of TMD-derived donor-acceptor hybrids in light energy harvesting and optoelectronic applications. Furthermore, the fundamental information obtained from the current results will benefit design strategies and impact the development of additional TMD-based hybrid materials to efficiently manage and perform in electron-transfer processes.

A new set of donor–acceptor (D–A) conjugates capable of undergoing ultrafast electron transfer were synthesized using 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (BODIPY)‐substituted phenothiazine, SM1–SM3, by a Pd‐catalyzed Sonogashira cross‐coupling reaction and a [2+2] cycloaddition–electrocyclic ring‐opening reaction. The incorporation of 1,1,4,4‐tetracyanobuta‐1,3‐diene (TCBD) and cyclohexa‐2,5‐diene‐1,4‐diylidene‐expanded TCBD (abbreviated as DCNQ=dicyanodiquinodimethane) in BODIPY‐substituted phenothiazine resulted in significant perturbation of the optical and electronic properties. The absorption spectrum of both SM2 and SM3 showed red shifted absorption as compared to SM1. Additionally, both SM2 and SM3 exhibited a distinct intramolecular charge‐transfer (ICT) transition in the near‐IR region more so for SM3. The electrochemical study revealed multi‐redox processes due to the presence of redox‐active phenothiazine, BODIPY, TCBD or DCNQ entities. Using data from spectral, electrochemical and computational studies, an energy‐level diagram was established to witness excited‐state electron‐transfer events. Finally, evidence of electron transfer and their kinetic information was secured from studies involving a femtosecond transient absorption technique. The time constants for excited‐state electron‐transfer events in the case of SM2 and SM3 were less than 5 ps revealing ultrafast processes.

The functionalization of MoS2 is of paramount importance for tailoring its properties towards optoelectronic applications and unlocking its full potential. Zinc phthalocyanine (ZnPc) carrying an 1,2‐dithiolane oxide linker was used to functionalize MoS2 at defect sites located at the edges. The structure of ZnPc‐MoS2 was fully assessed by complementary spectroscopic, thermal, and microscopy imaging techniques. An energy‐level diagram visualizing different photochemical events in ZnPc‐MoS2 was established and revealed a bidirectional electron transfer leading to a charge separated state ZnPc.+‐MoS2.−. Markedly, evidence of the charge transfer in the hybrid material was demonstrated using fluorescence spectroelectrochemistry. Systematic studies performed by femtosecond transient absorption revealed the involvement of excitons generated in MoS2 in promoting the charge transfer, while the transfer was also possible when ZnPc was excited, signifying their potential in light‐energy‐harvesting devices.

Usage of multimodular donor–acceptor systems capable of revealing tunable ground- and excited-state properties is gaining momentous interest for applications in light energy harvesting and optoelectronics. Here, we demonstrate conversion of a large-bandgap donor–acceptor–donor (D–A–D) type system, (triphenylamine–benzothiadizole–triphenylamine, TPA–BTD–TPA) into low-bandgap, unsymmetrical, D–A′–A–D and D–A′–A–A″–D type donor–acceptor systems by the insertion of tetracyano­butadiene (A′) or dicyanoquino­dimethane (A″) by [2 + 2] cycloaddition–retro-electrocyclization reactions. Because of the existence of strong charge transfer in the ground and excited states, these low-bandgap unsymmetrical donor–acceptor chromophores exhibit strong electronic absorption covering the visible and near-IR regions. Electrochemical, spectroelectrochemical, and computational studies are performed to evaluate their redox potentials and spectral characterization of oxidized/reduced species as well as to realize their electronic structures. Finally, the occurrence of ultrafast charge separation in these conjugates has been established from femtosecond transient absorption covering the visible–near-IR regions in polar and nonpolar solventsproperties relevant toward their optoelectronic applications.

The effect of acceptor strength on excited-state charge transfer (CT) and charge separation (CS) in central phenothiazine (PTZ)-derived symmetric 1 (PTZ-(TCBD-TPA) 2 ) and asymmetric 2 (PTZ-(TCBD/DCNQ-TPA) 2 ) push−pull conjugates, in which triphenylamine (TPA) acts as end capping and 1,1,4,4− tetracyanobuta−1,3−diene (TCBD) and cyclohexa−2,5−diene−1,4−ylidene−expanded TCBD (DCNQ) act as electron acceptor units, is reported. Due to strong push−pull effects, intramolecular CT was observed in the ground state, extending the absorption into the near-infrared region. Electrochemical, spectroelectrochemical, and computational studies coupled with energy-level calculations predicted both 1 and 2 to be efficient candidates for ultrafast CT. Subsequent femtosecond transient absorption studies along with global target analysis, performed in both polar and nonpolar solvents, confirmed such processes in which the CS was efficient in asymmetric 2, having both TCBD and DCNQ acceptors in polar benzonitrile, while in toluene, only CT was witnessed. This work highlights the significance of the number and strength of electron acceptor entities and the role of solvent polarity in multimodular push−pull systems to achieve ultrafast CS.

The covalent functionalization of MoS 2 with ap erylenediimide (PDI) is reported and the study is accompanied by detailed characterization of the newly prepared MoS 2-PDI hybrid material. Covalently functionalizedM oS 2 interfacing organic photoactive species has shown electron and/or energy accepting,energy reflecting or bi-directional electron accepting features.H erein, ar ationally designed PDI, unsubstituted at the perylene core to act as electron acceptor,f orces MoS 2 to fully demonstrate for the first time its electron donor capabilities.The photophysical response of MoS 2-PDI is visualized in an energy-level diagram, while femtosecond transient absorption studies disclose the formation of MoS 2 C +-PDIC À charge separated state.T he tunable electronic properties of MoS 2 ,a saresult of covalently linking photoactive organic species with precise characteristics,u nlock their potentiality and enable their application in light-harvesting and optoelectronic devices.

The functionalization of MoS 2 is of paramount importance for tailoring its properties towards optoelectronic applications and unlocking its full potential. Zinc phthalocyanine (ZnPc) carrying an 1,2-dithiolane oxide linker was used to functionalize MoS 2 at defect sites located at the edges.T he structure of ZnPc-MoS 2 was fully assessed by complementary spectroscopic,t hermal, and microscopyi maging techniques. An energy-level diagram visualizing different photochemical events in ZnPc-MoS 2 was established and revealed ab idirectional electron transfer leading to ac harge separated state ZnPcC + -MoS 2 C À .M arkedly,e vidence of the charge transfer in the hybrid material was demonstrated using fluorescence spectroelectrochemistry.Systematic studies performed by femtosecond transient absorption revealed the involvement of excitons generated in MoS 2 in promoting the charge transfer, while the transfer was also possible when ZnPc was excited, signifying their potential in light-energy-harvesting devices.

A new set of free‐base and zinc(II)‐metallated, β‐pyrrole‐functionalized unsymmetrical push–pull porphyrins were designed and synthesized via β‐mono‐ and dibrominated tetraphenylporphyrins using Sonogashira cross‐coupling reactions. The ability of donors and acceptors on the push–pull porphyrins to produce high‐potential charge separated states was investigated. The porphyrins were functionalized at the opposite β,β′‐pyrrole positions of porphyrin ring bearing triphenylamine push groups and naphthalimide pull groups. Systematic studies involving optical absorption, steady‐state and time‐resolved emission revealed existence of intramolecular type interactions both in the ground and excited states. The push–pull nature of the molecular systems was supported by frontier orbitals generated on optimized structures, wherein delocalization of HOMO over the push group and LUMO over the pull group connecting the porphyrin π‐system was witnessed. Electrochemical studies were performed to visualize the effect of push and pull groups on the overall redox potentials of the porphyrins. Spectroelectrochemical studies combined with frontier orbitals helped in characterizing the one‐electron oxidized and reduced porphyrins. Finally, by performing transient absorption studies in polar benzonitrile, the ability of push–pull porphyrins to produce charge‐separated states upon photoexcitation was confirmed and the measured rates were in the range of 109 s−1. The lifetime of the final charge separated state was around 5 ns. This study ascertains the importance of push–pull porphyrins in solar energy conversion and diverse optoelectronic applications, for which high‐potential charge‐separated states are warranted.