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Photofunctional materials based on donor-acceptor molecules have drawn intense attention due to their unique optical properties. Importantly, Systematic investigation of substitution effects on excited-state charge transfer dynamics of donor-acceptor molecules is a powerful approach for identifying application-relevant design principles. Here, by coupling phenothiazine (PTZ) at the ortho-, meta-, and para-positions of the benzene ring of benzophenone (BP), three regioisomeric BP-PTZ dyads were designed to understand the relationship between substituted positions and excited-state evolution channels. Ultrafast transient absorption is used to detect and trace the transient species and related evolution channels of BP-PTZ dyads at excited state. In a non-polar solvent, BP-o-PTZ undergoes the through-space charge transfer process to produce a singlet charge-transfer (1CT) state, which subsequently proceeds the intersystem crossing process and transforms into a triplet charge-transfer (3CT) state; BP-m-PTZ experiences intramolecular charge transfer (ICT) process to generate the 1CT state, which subsequently transforms into the 3CT state by the intersystem crossing (ISC) and finally converts into the local-excited triplet (3LE) state; as for BP-p-PTZ, only 3LE states can be detected after the ISC process from the 1CT state. On the other hand, the twisted ICT states are generated via twisted motion between the donor and acceptor for all BP-PTZ dyads or planarization of the PTZ unit in high polar solvents. The excited-state theoretical calculations unveil that the features of ICT and intramolecular interaction between the three dyads play a decisive role in determining the through-bond charge transfer and through-space charge transfer processes. Also, these results demonstrate that the excited-state evolution channels of PTZ derivatives could be modified by tuning the substituted positions of the donor-acceptor dyads. This study provides a deep perspective for the substitute-position effect on donor-acceptor-type PTZ derivatives. [ABSTRACT FROM AUTHOR]

An anion‐counterion strategy is proposed to construct organic mono‐radical charge‐transfer cocrystals for near‐infrared photothermal conversion and solar‐driven water evaporation. Ionic compounds with halogen anions as the counterions serve as electron donors, providing the necessary electrons for efficient charge transfer with unchanged skeleton atoms and structures as well as the broad red‐shifted absorption (200–2000 nm) and unprecedented photothermal conversion efficiency (~90.5 %@808 nm) for the cocrystals. Based on these cocrystals, an excellent solar‐driven interfacial water evaporation rate up to 6.1±1.1 kg ⋅ m−2 ⋅ h−1 under 1 sun is recorded due to the comprehensive evaporation effect from the cocrystal loading in polyurethane foams and chimney addition, such performance is superior to the reported results on charge‐transfer cocrystals or other materials for solar‐driven interfacial evaporation. This prototype exhibits the great potential of cocrystals prepared by the one‐step mechanochemistry method in practical large‐scale seawater desalination applications. [ABSTRACT FROM AUTHOR]

Vinyldiazo compounds are one of the most important synthons in the construction of a cyclic ring. Most photochemical transformations of vinyldiazo compounds are mainly focusing on utilization of their C═C bond site, while reactions taking place at terminal nitrogen atom are largely unexplored. Herein, a photocatalytic cascade radical cyclization of LBRs with vinyldiazo reagents through sequential B─N/C─N bond formation is described. The reaction starts with the addition of LBRs (Lewis base–boryl radicals) at diazo site, followed by intramolecular radical cyclization to access a wide range of important boron‐handled pyrazoles in good to excellent yields. Control experiments, together with detailed mechanism studies well explain the observed reactivity. Further studies demonstrate the utility of this approach for applications in pharmaceutical and agrochemical research. [ABSTRACT FROM AUTHOR]

A new phosphine‐catalyzed reaction of α‐substituted allenes with aryl imines, in stark contrast to classic cycloaddition reactions, has been developed. This reaction delivers valuable highly functionalized itaconimides with excellent stereoselectivities by a new «un‐cyclizing» reaction mode involving β′‐carbon of α‐substituted allenes. Moreover, the present «un‐cyclizing» reaction can also be carried out in a one‐pot fashion and scaled up to the gram scale by using aryl aldehydes, without the need to isolate the aryl imines. Mechanistic studies and control experiments reveal the crucial role of H2CO3 for the present reaction mode. In addition, density functional theory (DFT) calculations were performed to understand the possible mechanism. [ABSTRACT FROM AUTHOR]

Double‐bond photoswitching molecules typically can undergo trans→cis photoisomerization, but their photoisomerization mechanisms in the solid state have been rarely reported. Herein, the excited‐state evolutions of trans‐azobenzene (AB), trans‐stilbene (TS), and N‐benzylideneaniline (NBA) are studied to unveil the relationship between the double‐bond photoswitching molecules and the photoisomerization kinetics in the solution phase and in nanocrystal suspensions (NCS). The photoisomerization rate of NBA is the fastest among these three molecules in the solution phase due to its most apparent single‐bond feature of the central double bond in the S1 state. The free space ordered crystal configuration boosts the photoisomerization rates of AB and TS in NCS to be faster than that of the solution phase because the hindrance of the wrapping solvent is eliminated in the crystals. In contrast, when NBA is prepared into NCS, it becomes distorted into a nonplanar structure because of the asymmetrical C‐H···π interactions, resulting in NBA having a large spin‐orbital coupling (SOC) value which opens the intersystem crossing channel to generate the triplet state instead of undergoing photoisomerization in solution. Therefore, this work reveals that the crystal configuration and the molecular structure may critically determine the photophysical properties of photoswitching materials. [ABSTRACT FROM AUTHOR]

Inspired by the concept of ionic charge‐transfer complexes for the Mott insulator, integer‐charge‐transfer (integer‐CT) cocrystals are designed for NIR photo‐thermal conversion (PTC). With amino‐styryl‐pyridinium dyes and F4TCNQ (7,7',8,8'‐Tetracyano‐2,3,5,6‐tetrafluoroquinodimethane) serving as donor/acceptor (D/A) units, integer‐CT cocrystals, including amorphous stacking "salt" and segregated stacking "ionic crystal", are synthesized by mechanochemistry and solution method, respectively. Surprisingly, the integer‐CT cocrystals are self‐assembled only through multiple D−A hydrogen bonds (C−H⋅⋅⋅X (X=N, F)). Strong charge‐transfer interactions in cocrystals contribute to the strong light‐harvesting ability at 200–1500 nm. Under 808 nm laser illumination, both the "salt" and "ionic crystal" display excellent PTC efficiency beneficial from ultrafast (∼2 ps) nonradiative decay of excited states. Thus integer‐CT cocrystals are potential candidates for rapid, efficient, and scalable PTC platforms. Especially amorphous "salt" with good photo/thermal stability is highly desirable in practical large‐scale solar‐harvesting/conversion applications in water environment. This work verifies the validity of the integer‐CT cocrystal strategy, and charts a promising path to synthesize amorphous PTC materials by mechanochemical method in one‐step. [ABSTRACT FROM AUTHOR]

Effective utilization of solar energy through cocrystal strategy is still a considerable challenge. Herein, the ternary cocrystal strategy is subtly applied to broaden the absorption of cocrystals, resulting in an efficient solar photothermal conversion (PTC). Specifically, the donors of triphenylene (T) and perylene (P) and guest molecules anthracene (AT), pyrene (PY), and perylene (P) are self‐assembled with 7,7,8,8‐tetracyanoquinodimethane (TCNQ) to obtain five ternary cocrystals (AT‐T‐TCNQ, PY‐T‐T‐TCNQ, AT‐P‐TCNQ, PY‐P‐TCNQ, and P‐P‐TCNQ). The PTC of ternary cocrystals can be regulated by changing the number of benzene rings of donor and guest molecules, which may be attributed to the π–π and C–H···π intermolecular interactions. Femtosecond transient absorption and excited‐state theoretical calculations confirm that the intense π–π stacking interactions facilitate the light‐harvesting capability, while the weak C–H···π interactions are conducive to molecular stacking loosening and thus facilitate the rotation of C(C ≡ N)2, which promotes nonradiative transition to achieve the efficient PTC. As expected, the PTC efficiencies of AT‐T‐TCNQ, PY‐T‐TCNQ, AT‐P‐TCNQ, PY‐P‐TCNQ, and P‐P‐TCNQ are 59.62%, 63.07%, 81.72%, 79.06%, and 87.72%, respectively, under 808 nm irradiation. Due to the P‐P‐TCNQ having excellent near‐infrared PTC efficiency, it is applied in a solar‐driven interfacial heating evaporation system, gaining a decent evaporation efficiency (83.1%). [ABSTRACT FROM AUTHOR]

Donor and acceptor (D–A) compounds based on benzophenone (BP) and carbazole (Cz) were recently reported to exhibit an extraordinary long afterglow phosphorescence in the solid state. However, the BP derivatives' mechanism of long afterglow phosphorescence is obscure. BP-o-Cz, BP-m-Cz, and BP-p-Cz were designed by coupling Cz at the ortho-, meta- and para-positions of the BP's benzene ring to uncover the excited-state evolution of BP-Cz molecules. Femtosecond and nanosecond transient absorption and excited-state theoretical calculations were carried out to detect and trace the photophysical process of BP-Cz dyads. After the excitation, all dyads experience intramolecular charge transfer (ICT) and intersystem crossing (ISC) processes. The resulting charge-transfer (1CT and 3CT) state of BP-o-Cz will decay to the ground state directly and quickly via the fast charge recombination (CR) process, which may be caused by through-space D–A interaction due to the enforced proximity between BP and Cz. In contrast, for BP-m-Cz and BP-p-Cz dyads, the complete separation of HOMOs and LUMOs leads to extended ICT and slow CR processes, producing an obvious Cz cation radical intermediate and an ultralong-lived triplet state species after the 3CT. Herein, we demonstrated that the excited-state evolution channels could be modified by tuning the substituted positions of D–A dyads. This may pave the way for designing efficient D–A type luminescent materials. [ABSTRACT FROM AUTHOR]

Long persistent luminescence (LPL) can store light energy in excited states and gradually release it as light. Organic host–guest systems provide a good platform for LPL, and single‐color LPL is often achieved while multicolor LPL is challengeable. Here host–guest supramolecular complexes are presented with dual LPL emissions: thermally activated delayed fluorescence (TADF) (≥100 ms) and room temperature phosphorescence (RTP). A space charge transfer from α‐cyclodextrin to diphenylacetylene (DPA) with long‐range transportation (2.32 mm) carrier along DPA strand in the supramolecular complexes is attributed to generate the TADF and RTP. Fortunately, these supramolecular complexes are readily fabricated from α‐cyclodextrin and DPA or DPA derivatives. The gradient color is observed after removing UV excitation. Furthermore, the hydrophobic property inside α‐cyclodextrin makes the LPL appear by water shedding and disappear by organic solvent infiltration, showing the character of a "switch." This host–guest space charge transfer strategy paves a way to design LPL materials. [ABSTRACT FROM AUTHOR]

By utilizing the bipolarity of 1,2‐diphenylphenanthroimidazole (PPI), two types of asymmetrical tripartite triads (PPI‐TPA and PPI‐PCz) were designed with triphenylamine (TPA) and 9‐phenylcarbazole (PCz). These triads are deep‐blue luminescent materials with a high fluorescence quantum yield of nearly 100 %. To trace the photophysical behaviors of these triads, their excited‐state evolution channels and interchromophoric interactions were investigated by ultrafast time‐resolved transient absorption and excited‐state theoretical calculations. The results suggest that the electronic nature, asymmetrical tripartite structure, and electron–hole distance of these triads, as well as solvent polarity, determine the lifetime of intramolecular charge transfer (ICT). Interestingly, PPI‐PCz triads show anti‐Kasha ICT, and the charge‐transfer direction among the triads is adjustable. For the PPI‐TPA triad, the electron is transferred from TPA to PPI, whereas for the PPI‐PCz triad the electron is pushed from PPI to PCz. Exploration of the excited‐state ICT in these triads may pave the way to design better luminescent materials in the future. [ABSTRACT FROM AUTHOR]

Due to the rapid development of non-fullerene acceptors (NFAs), the efficiency of organic solar cells is steadily being improved. The stability of organic solar cells also is expected to be enhanced with the introduction of the NFAs, yet the stability of NFAs themselves have been less investigated to date. In this paper, the stability of a set of typical NFAs was studied in situ employing photoelectron spectroscopy. The studied molecules show higher resistance to water vapor and thermal stress compared to fullerenes. For water vapor exposure, the highest occupied molecular orbital (HOMO) of NFAs undergoes only minor and reversible changes and the NFAs/substrate work function stays constant. Exposure to oxygen gas significantly modified the electronic structure of the NFAs and the effect was only partially reversible by annealing. However, the presence of water vapor was shown to slow down the degradation caused by oxygen. This is in stark contrast to fullerenes that undergo irreversible degradation upon water vapor exposure. [ABSTRACT FROM AUTHOR]

"D-A pairs" as the basic "micro-stacking units" in cocrystals guarantee strong donor-acceptor interactions and excellent photothermal performance. Dynamics of excited states, mechanochemistry, integer-charge-transfer, intermolecular hydrogen bond, photo-thermal conversion Keywords: dynamics of excited states; mechanochemistry; integer-charge-transfer; intermolecular hydrogen bond; photo-thermal conversion EN dynamics of excited states mechanochemistry integer-charge-transfer intermolecular hydrogen bond photo-thermal conversion 1 1 1 07/25/23 20230721 NES 230721 B The Front Cover b shows integer-charge-transfer cocrystals are self-assembled via multiple intermolecular hydrogen bonds with one electron transferred from donor to acceptor unit for high-efficiency (~87 %) NIR photothermal conversion. [Extracted from the article]