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The dynamics of excited‐state charge transfer (CT) in second near‐infrared (NIR‐II) fluorophore proceeds with conformational change that govern fluorescence. Unveiling the relationship between CT dynamics and conformational change in excited state is of great fundamental significance in optimizing NIR‐II fluorescence but remains less explored. This study unveils the pivotal role of large conformational change in promoting the evolution of emissive CT state into nonemissive CT state in NIR‐II fluorophore (CA‐BBT). Spectroscopic and computational results reveal that large conformational rotation/twisting leads to a pronounced increase in the CT character in excited state. This heightened CT character in CA‐BBT enables a rapid evolution of emissive CT state into a nonemissive CT state within 1.4 ps, as observed by ultrafast spectroscopy. Subsequently, this nonemissive state dominates nonradiative decay, resulting in very low NIR‐II fluorescence. Preventing such detrimental evolution by constraining the conformational dynamics of CA‐BBT results in a 10‐fold enhancement of NIR‐II fluorescence, enabling high‐resolution dynamic visualization of vasculature within osteosarcoma. This study offers a profound understanding of the relationship between CT dynamics and conformational changes in NIR‐II fluorescence, presenting innovative perspectives to develop bright NIR‐II fluorophores. [ABSTRACT FROM AUTHOR]

A series of reported Pt(II) carbene complexes possibly have the ability to serve as the new generation of blue emitters in luminescent devices because of their narrow emission spectra, high photoluminescence quantum yields (PLQYs), and rigid molecular skeleton. However, the combination of all carbene ligands with different multidentate structures will affect the overall planarity and horizontal dipole ratio to varying degrees, but the specific extent of this effect has not previously been analyzed in detail. In this work, density functional computation is used to study a class of platinum tetracarbene bidentate complexes with similar absorption and emission band characteristics, which is the main reason for the remarkable difference in quantum efficiency due to subtle differences in electronic states caused by different ligands. From the calculation results, the major reason, which results in significantly decrease in quantum efficiency for [Pt(cyim)2]2+, is that [Pt(cyim)2]2+ can reach the non-radiative deactivation metal-centered d-d excited state through an easier pathway compared with [Pt(meim)2]2+. The result, based on changes in the dihedral angle between ligands, can achieve the goal of improving and designing materials by adjusting the degree of the dihedral angle. (meim: bis(1,1′-dimethyl-3,3′-methylene-diimidazoline-2,2′-diylidene); cyim: bis(1,1′-dicyclohexyl-3,3′-methylene-diimidazoline-2,2′-diylidene). [ABSTRACT FROM AUTHOR]

Photo-controlled self-assembly of nanoparticles (NPs) is an advanced and promising approach to address a series of material issues from the molecular level to the nano/micro scale, owing to the fact that light stimulus is typically precise and rapid, and can provide contactless spatial and temporal control. The traditional photo-controlled assembly of NPs is based on photochemical processes through NPs modified by photo-responsive molecules, which are realized through the change in chemical structure under irradiation. Moreover, photoexcitation-induced assembly of NPs is another promising physical strategy, and such a strategy aims to employ molecular conformational change in the excited state (rather than the chemical structure) to drive molecular motion and assembly. The exploration and control of NP assembly through such a photo-controlled strategy can open a new paradigm for scientists to deal with "bottom-up" behaviors and develop unprecedented optoelectronic functional materials. [ABSTRACT FROM AUTHOR]

It is shown that, like conventional diffuse fluorescence spectra and despite the complex mechanism of formation of the excited state, the chemi- and bioluminescence spectra contain information about the frequency of the purely electronic (vertical) transition of the emitting molecules and the degree of homogeneity of their ensemble. As in the case of ordinary diffuse luminescence spectra, the frequency of a purely electronic transition is shifted significantly toward the short wavelength side (by almost the half-width of the band) from the maximum of the fluorescence spectrum. An example of the separation of the overlapping spectra using the position of a short-wavelength purely electronic transition is presented. [ABSTRACT FROM AUTHOR]

In this review, we have attempted to briefly summarize the influence of an external electric field on an assembly of tautomeric molecules and to what experimentally observable effects this interaction can lead to. We have focused more extensively on the influence of an oriented external electric field (OEEF) on excited-state intramolecular proton transfer (ESIPT) from the studies available to date. The possibilities provided by OEEF for regulating several processes and studying physicochemical processes in tautomers have turned this direction into an attractive area of research due to its numerous applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • The excited states of three blue emitters are manipulated from CT to HLCT. • Blue vacuum-evaporated HLCT OLEDs exhibit maximum EQE of 7.52%. • The solution-processed HLCT OLED shows a high maximum EQE of 6.49%. • Very low efficiency roll-offs of 0.8% and 3.7% at 100 and 1000 cd m−2 are achieved. Manipulating the excited states of organic luminescent materials can efficiently improve the utilization of both singlet and triplet excitons for developing high-performance organic light-emitting diodes (OLEDs), but the issue remains difficult due to the lack of well-controlled ways. Here, we proposed a molecular design strategy of excited state manipulation from charge-transfer (CT) to hybridized local and charge-transfer (HLCT) via adjusting the cyano position on pyridine acceptor. The meta -substituted PyAn4CN is mainly composed of a CT component, while the para -substituted PyAn5CN is endowed with a HLCT component. On further extending the conjugation of PyAn5CN by inserting a benzene unit between the pyrene and anthracene core, the HLCT character is preserved in PyPhAn5CN , accompanied by a faster radiative decay. Consequently, the vacuum-evaporated OLEDs exhibit blue electroluminescence (EL) with the emission peaks in the range of 455–460 nm and high external quantum efficiency (EQE) up to 7.52%, together with well-suppressed efficiency roll-offs of 0.8% and 3.7% at the luminance of 100 and 1000 cd m-2, respectively. More importantly, the solution-processed device shows an excellent performance with EQE of 6.49%, which is one of the best results in the solution-processed HLCT OLEDs. Our results clearly indicate that the formation of HLCT state is an efficient way to realize high-efficiency blue electrofluorescence. [ABSTRACT FROM AUTHOR]

Vacuum ultraviolet (VUV) based advanced oxidation processes (AOPs) recently attracted widespread interests. However, the role of UV 185 in VUV is only considered to be generating a series of active species, while the effect of photoexcitation has long been overlooked. In this work, the role of UV 185 induced high-energy excited state for the dephosphorization of organophosphorus pesticides was studied using malathion as a model. Results showed malathion degradation was highly related to radical yield, while its dephosphorization was not. It was UV 185 rather than UV 254 or radical yield that was responsible for malathion dephosphorization by VUV/persulfate. DFT calculation results demonstrated that the polarity of P-S bond was further increased during UV 185 excitation, favoring dephosphorization while UV 254 did not. The conclusion was further supported by degradation path identification. Moreover, despite the fact that anions (Cl-, SO 4 2- and NO 3 -) considerably affected radical yield, only Cl- and NO 3 - with high molar extinction coefficient at 185 nm significantly affected dephosphorization. This study shed light on the crucial role of excited states in VUV based AOPs and provided a new idea for the development of mineralization technology of organophosphorus pesticides. [Display omitted] • High-energy excited states rather than radical yield dominated OPs mineralization. • Photoexcitation altered the regioselectivity of radical attack. • UV 185 weakened P–S bond, which decided dephosphorization, while UV 254 cannot. • Anions affected mineralization via UV 185 absorption rather than radical quenching. [ABSTRACT FROM AUTHOR]

[Display omitted] • electronic properties of γ-graphyne cluster models converge rapidly. • electronic properties of γ-graphyne clusters have a low dependence on vacancy defects. • γ-graphyne is an efficient electron acceptor (low LUMO and ability to delocalize excess charge). • photoinduced electron transfer from electron donors to γ-graphyne is efficient and fast. The search for new materials is constantly ongoing. Recently, a two-dimensional carbon allotrope , γ-graphyne , has been synthesized with a unified crystalline structure. Because of its low LUMO and excellent electron mobility, it appears to be a promising electron acceptor for photovoltaic applications. Here we report an analysis of the electronic properties of model van der Waals complexes of γ-graphyne with several partners of different electronic nature. We show that photoinduced electron transfer from electron-donating partners to γ-graphyne is favorable and occurs on nano to picosecond time scale. In contrast, electron transfer from γ-graphyne to strong electron acceptors is unlikely. Our results open perspectives for the future application of γ-graphyne in photovoltaic devices. [ABSTRACT FROM AUTHOR]

• New tris(trifluoromethyl)germylethynyl derivative of biphenyl with ferrocenylethnyl donor group have been prepared. • Intramolecular energy and electron transfer have been investigated in the unsymmetrical 4-ferrocenylethnyl-4´-[tris(trifluoromethyl)germylethynyl]biphenyl molecule. • Vacant Ge 4d atomic orbitals play a key role in this phenomenon. Unsymmetrical 4,4′-biphenyl derivative with tris(trifluoromethyl)germylethynyl ‒C C‒Ge(CF 3) 3 and ferrocenylethynyl Fc‒C C‒ substitutes have been prepared (21), its properties have been studied and compared with those full non-fluorinated analogue of trimethylgermylethynyl ‒C C‒Ge(CH 3) 3 compound (20). UV-visible, absorption, steady state, and time-resolved fluorescence spectra in solution for these germanium and a number of similar compounds (15 - 17, 22) have been investigated. The process of photoinduced electron transfer from the π-conjugated system to the germanium center is confirmed for 21 , as well as for the first time discovered earlier [19] in the 4-biphenyl ‒C C‒Ge(CF 3) 3 molecule (9). It was found that the lifetime of the radical-ion pair 21 in the excited state (k CR2 = 1.2 × 105 s-1) is approximately an order of magnitude longer than for 9 , which can be explained by the stabilizing effect of the electron donor Fc‒C C‒ group. Density-functional theory (DFT) computations was used to calculate the optimized geometry of 21 in excited state, and two main bands in the emission spectrum at laser excitation (340 and 386 nm) an excellent fit to the experimental data. An additional data on the nature of the (CF 3) 3 Ge group, including geometry, electronegativity, and contributions 4d AOs of germanium into lowest unoccupied molecular orbital (LUMO) in a wide range of fluorinated and non-fluorinated compounds were also calculated. The molecular structure of compound 21 was determined by X-ray structural analysis. In the crystal lattice of 21 , numerous intermolecular F‧‧‧F interactions shortened in comparison with the van der Waals radii were detected, which leads to the formation of quasi-two-dimensional fluorinated layers in crystals. The unsymmetrical triad of 4-ferrocenylethynyl-4΄-[tris(trifluoromethyl)germylethynyl]biphenyl exhibits stepwise intramolecular energy and charge transfer into (CF 3) 3 Ge group upon laser excitation at 266 nm. This confirms the previously discovered effect for a similar compound of 4-[tris(trifluoromethyl)germylethynyl]biphenyl containing no ferrocenylethynyl group. The total quantum yield of the state with completely separated charges is 33%. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Regulating excited-state properties for high brightness DR/NIR fluorophores. • Both fluorophores show aggregation-induced emission performance. • The PLQY arrives to 56 % with maximal emission of 692 nm at aggregation. Deep red/Near-infrared (DR/NIR) emitters with high photoluminescent quantum yield (PLQY) in the aggregate state are still challenge for achieving highly efficient non-doped organic light emitting diodes (OLEDs). Herein, we utilize the methodology of regulating excited-state property to adjust the proportion of radiative and nonradiative transition at aggregation, three aggregation-induced emission (AIE) active emitters (TNZNp, TNZTPAN and TNZTPEDA) with diverse sum of benzene ring rotors are prepared. TNZTPEDA with more rotors suffers from fast nonradiative transition which leads to the low fluorescent efficiency in the unimolecular and aggregate levels. Oppositely, decreasing rotors to enhance obviously solid-state PLQY of TNZNp, but the radiative transition rate is still lower than the nonradiative rate. After introducing rotational electronic donor to improving locally excited-state proportion and suppress intermolecular interaction, simultaneously, TNZTPAN has the best PLQY of 56 % due to the faster radiative transition than nonradiative transition at aggregation. Three emitters are used to manufacture non-doped OLEDs, TNZTPAN shows the maximal electroluminescence peaking at 692 nm with Commission International de L'Eclairage coordinates of (0.68, 0.30), the external quantum efficiency of 3.54 % represents a higher level among the reported non-doped DR/NIR-type OLEDs. The results of this work demonstrate the feasibility of regulating excited-state property to prepare highly bright emitters, which plays important role in designing organic DR/NIR emitters with high fluorescent efficiency at aggregation in the future. [ABSTRACT FROM AUTHOR]

The efficiency and mechanism of heterogeneous catalytic O 3 and UV/O 3 for municipal solid waste (MSW) incineration leachate advanced treatment was systematically compared. Prior to comparison, catalyst used in heterogenous catalytic O 3 and operation parameters for each technology were optimized. The COD removal of CuO@Al 2 O 3 /O 3 under its optimal parameters was 57.2%, which failed to meet the standard (≥75%). In contrast, the COD removal by UV/O 3 could be 82.3%. The superior efficiency of UV/O 3 over CuO@Al 2 O 3 /O 3 could be summarized into three aspects: (I) Cu bounded ·OH (≡Cu–O·) preferentially attacked hydrophilic groups, while free hydroxyl radical (·OH) was non-selective, thus UV/O 3 exhibited a unique three-stage mechanism; (II) The oxidation potential of ≡Cu–O· was higher than that of ·OH, therefore was more vulnerable to the negative effect of radical self-quenching; (III) The existence of UV-induced excited states made organics in UV/O 3 more active than in CuO@Al 2 O 3 /O 3 system, thus high concentration of anions enhanced COD removal in UV/O 3 but affected that in CuO@Al 2 O 3 /O 3. The study further revealed the characteristics of heterogeneous catalytic O 3 and UV/O 3 , and UV induced excited state should be considered in UV-based advanced oxidation processes (AOPs). [Display omitted] • UV/O 3 was more efficient than CuO@Al 2 O 3 /O 3 for MSW incineration leachate treatment. • CuO@Al 2 O 3 /O 3 had stronger mineralization effect but suffered the problem of self-quenching. • UV induced excited state explained the absence of self-quenching in UV/O 3. • O 3 , ≡Cu–O·, ·OH had different selectivity, and UV/O 3 exhibited a unique three-stage mechanism. • High salinity enhanced the mineralization ability of UV/O 3 due to the presence of UV induced excited state. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lock/unlock strategy proposed to manipulate excited states and photophysical properties of TADF materials. • Efficient TADF emitters with high PLQYs (up to 0.91), short TADF lifetimes and excellent stability and film-quality. • High-performance OLED with EQE beyond 25%. Thermally activated delayed fluorescent (TADF) materials have drawn widespread attentions due to their great potential for practical applications in organic light-emitting diodes (OLEDs). Deep understanding of the structure-excited state-photophysical property relationships is a key to rationally design TADF emitters. Herein, two new TADF molecules, TBP-DPXZ and TBQ-DPXZ, which consist of locked (triptycene-fused dibenzophenazine) and unlocked (triptycene-fused 2, 3-diphenylquinoxaline) electron-acceptors respectively and phenoxazine electron donors are reported. The comparative study reveals that the lock/unlock strategy could substantially manipulate the lowest locally excited (LE) and charge transfer (CT) states of these emitters via changing the acceptor strength, structural rigidity, and conjugation length, and in turn lead to significantly different photoluminescence (PL) and electroluminescence (EL) performance. It is notable that the unlocked molecule TBQ-DPXZ emits efficient green fluorescence with photoluminescence quantum yield of 91% and TADF lifetime of 3.6 μs in doped film. The doped OLED based on TBQ-DPXZ achieves an external quantum efficiency (EQE) of 25.1%, a current efficiency (CE) of 79.7 cd/ A, a power efficiency (PE) of 80.0 lm/W, and a maximum luminance of 18400 cd/m2, which are better than those of the TBP-DPXZ-based device and are among the best results reported so far for green TADF-OLEDs. [ABSTRACT FROM AUTHOR]

• Firstly locate a more reasonable structure for the product of DHADC reacted with CN−. • A new fluorescence quenching mechanism for DHADC has been proposed. • Photo-induced hydrogen bonding variations have been explored. In this work, we investigated the fluorescence mechanism of the probe (E)-3-((4-(diethylamino)-2-hydroxybenzylidene)amino)-2,3-dihydrothiophene-2-carboxamide (DHADC) for both Zn2+ and CN− by using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. Utilizing the constructed potential energy curves both in the ground and excited states as a function of the distance of N2···H1, the proton transfer process of DHADC has been explored. According to the calculated spectra, another more reasonable structure of DHADC-CN for the product of DHADC responding to CN− has been proposed. All of the simulated absorption and emission spectra in this work are in agreement well with those in the experiment. Furthermore, the excited state decay picture and the fluorescence quenching mechanism of DHADC , as well as the fluorescence mechanism for Zn2+ and CN− have been fully explored. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermochromic excited state dipole moment determination. • Discussion on state mixing in bicyclic chromophores under electric field influences. • Discussion of problems using thermochromic fluorescence spectroscopy. The excited state dipole moment of the lowest excited singlet state of 2,3-benzofuran in ethylacetate solution is determined using thermochromic spectroscopy and compared to the values which are obtained for the isolated molecule from electronic Stark spectroscopy (Hebestreit et al., 2020) and to the results of ab initio calculations at coupled cluster level of theory. It is shown that the dipole moment from thermochromic shifts in solution deviates considerably from that of the isolated molecule. This finding can be traced back to a field induced mixing by the strong reaction field of the solvent, which exceeds the external Stark field applied in gas phase measurements by a factor of 10.000. Depending on the dipole moments of the perturbing state and its energy gap to the excited state, dipole moments from thermochromic shifts (and consequently also of solvatochromic shifts) might be considerably different to gas phase values. However, the alteration of the electronic configuration of the molecule via the reaction field of the solvent can be deperturbed in the high-field limit. [ABSTRACT FROM AUTHOR]

The 4-functionalized 6,6′-dimethyl-3,3′-dihydroxy-2,2′-bipyridine dyes (BP(OH) 2 -Rs) have exhibited dienol and diketo emissions. The optimum geometrical structures for ground, singlet and triplet excited states are computed by DFT/B3LYP/6–31++G that showed the planarity of BP(OH) 2 -Rs structure. The emission spectra of the molecules are determined in the gas-phase at singlet and triplet excited states using CIS/6–31++G. The theoretical calculations are carried out for BP(OH) 2 -Rs to understand the impact of different substituents (R = –H (I), –Br (II), –TMS (III), –C2H (IV), –terpyridine (V) and –bodipy (diazaboraindacene) (VI)) on excited-state intramolecular proton transfer (ESIPT) in singlet and triplet excited states. Based on the calculations, the concerted diproton transfer proceeds in the triplet excited state, in which nπ* state has a significant participation in ESIPT. The spectral variation at ESIPT emission of BP(OH) 2 -Rs is influenced by the electron-acceptor ability of the substituents. The compound V revealed a higher spectral intensity compared to the others. From the comparison with the experimental data, the molecule V is almost planar agreed with the X-ray structure and trend variation of wavelengths. The molecule VI contains bodipy chromophore that excitation energy transfers completely from BP(OH) 2 core to a bodipy substituent, leading to emission from the lowest-lying bodipy substituent, and consequently, ESIPT does not occur for this dye. [Display omitted] • Effects of different substituents in BP(OH) 2 -Rs on excited-state intramolecular proton transfer (ESIPT) was examined. • The geometrical structures for ground, singlet excited, and triplet excited states were optimized by DFT/B3LYP/6–31++G. • The emission spectra of the molecules are determined in the gas-phase via CIS/6–31++G. • The spectral variation is influenced by the electron-acceptor ability of the substituents. [ABSTRACT FROM AUTHOR]