Photoactive Naphthalene Diimide Functionalized Titanium-Oxo Clusters with High Photoelectrochemical Responses

Photoactive functionalized titanium-oxo clusters(TOCs)are regarded as an important model compound for dye-sensitized titanium dioxide solar cells.However,the dyes used for sensitizing TOCs are still limited.Herein,two cyclic TOCs are reported,namely,[Ti_(6)(μ_(3)-O)_(2)(Oi-Pr)_(8))(LA)_(2)]·i-PrOH(S1)and[Ti_(6)(μ_(3)-O)2(Oi-Pr)_(8))(LV)_(2)]·i-PrOH(S2),which are functionalized by photoactive naphthalene diimide(NDI)chromophores.Their molecular structures and photophysical and photochemical properties were systematically studied.As shown by ultraviolet-visible(UV-vis)spectra and photocurrent study results,the band gap and the photocurrent response of S1 and S2 were derived from NDI ligands which extend the absorption edge of S1 and S2 approaching 500 nm and afford high photocurrent densities of 2.12μA/cm^(2)and 1.95μA/cm^(2)for S1 and S2,respectively,demonstrating the significance of the photoactive ligand in modulating photoresponse of TOCs.This work is expected to enrich the structural library of photoactive TOCs and provide insights into understanding the structure-property relationships of sensitized clusters.

Perylene diimide self-assembly: From electronic structural modulation to photocatalytic applications

As an emerging organic semiconductor,perylene diimide(PDI)self-assembly has attracted tremendous attention in the aspects of solar cells,sensors,fluorescence probes and n-transistors,etc.In term of photocatalysis,various photocatalysts based on PDI self-assembly exhibit some unique properties,such as intrinsicΠ-Πstacking structure,fast internal charge transfer,band-like electronic structure,flexible structural modifiability,well-defined morphological adjustability and excellent light absorption.This paper mainly presents recent progress on PDI self-assembly regarding how to regulate the electronic structure of PDI self-assembly.In addition,the photocatalytic applications of PDI self-assembly and its complexes were reviewed,such as environmental remedy,energy productions,organic synthesis and photodynamic/photothermal therapy,further highlighting related photocatalytic mechanisms.Finally,the review contents and some perspectives on photocatalytic research of PDI selfassembly were summarized,and some key scientific problems were put forward to direct related photocatalytic research in future.

Recent advances in rylene diimide polymer acceptors for all-polymer solar cells

In recent years, a large library of n-type polymers have been developed and widely used as acceptor materi- als to replace fullerene derivatives in polymer solar cells （PSCs）, stimulating the rapid expansion of research on so-called all-polymer solar cells （aPSCs）. In particular, rylene diimide-based n-type polymer acceptors have attracted broad research interest due to their high electron mobility, suitable energy levels, and strong light-harvesting ability in the visible region. Among various polymer acceptors, rylene diimide-based poly- mers presented best performances when served as the acceptor materials in aPSCs. Typically, a record power conversion efficiency （PCE） of 7.7% was very recently achieved from an aPSC with a rylene diimide polymer derivative as the acceptor component. In this review, we highlight recent progress of n-type polymers orig- inated from two significant classes of rylene diimide units, namely naphthalene diimide （NDI） and perylene diimide （PDI）, as well as their derivatives for aPSC applications.

Effect of Fluorination on Aggregate Structure of Perylene Diimide

The effect of fluorination on the aggregate structure of a novel fluorinated perylene diimide, N, N'-diperfluorophenyl-3, 4, 9, 10-perylenetetracarboxylic diimide 1, was investigated by UV-Vis absorptions and the conformation simulations from AM1 semi-empirical quantum mechanics modeling. The results showed that in the solid film 1 molecules stacked with the perfluorinated phenyl groups straightly over or below the perylene cores of the adjacent 1 molecules.

Synthesis and Fluorescence Quenching of Copolymer Containing3, 4, 9, 10-Perylenetetracarboxyl Diimide Side Chains

A photoluminescence material, copolymer of N-vinylcarbazole (VCz) and N,N'- bisallyl-3, 4. 9, 10-ferylenetetracarboxyl diimide (APTC) chromophores P(VCz-APTC) was synthesized. The fluorescence quenching of P(VCz-APTC) by fullerene (C-60) and triethylamine was also studied.

Effects of 1,7-Bromine Substitution at Bay Area on Self-assembly Behavior and Photo Physical Properties of Perylene Diimide

N,N'-bis( n-dodecyl)-3,4: 9,10-tetracarboxyl-diimide( 1,7-H-PDI-C12) and its bay position 1,7-Br substituted derivative have been synthesized and characterized by1H-NMR,13C-NMR,FT-IR,and X-ray diffraction( XRD). A comparison of the two samples by measuring their photo physical properties using UV visible absorption and fluorescence emission spectra revealed that bay substitutions of bromine do not have significant effect on the perylene diimide( PDI) photo physical properties in solution. However,the solid state fluorescence properties were enhanced by brominating at bay areas. The solid fluorescence quantum yield of 1,7-Br-PDI-C12 was 2. 83%( Фf= 2. 83%) and 1,7-H-PDI-C12 was only 0. 02%( Фf= 0. 02%). This behavior was also reflected in the steady-state fluorescence spectra. This work shows that solid state photo physical properties of PDI could be improved without changing the other properties by simply using bromine substitution at bay areas. These types of materials are useful intermediate for further synthesis of PDI with tunnable optoelectronic properties.

Synthesis and Crystal Structure of N,N′-4-aminomethyl-pyromellitic diimide

The title compound N,N′-4-aminomethyl-pyromellitic diimide （4-pmpmd） crystallizes in monoclinic, space group P21/c with a = 4.785（1）, b = 6.200（1）, c = 29.907（2） A, β = 93.583（11）°, V= 885.5（2） A^3, Dc = 1.494 g/cm^3, Z= 2, C22H14N4O4, Mr = 398.37,/t（MoKα） = 0.106 mm^-1 and F（000） = 412, and its structure was refined to R = 0.0469 and wR = 0.1017 for 1194 observed reflections （F0 〉 4σ（F0））. The X-ray diffraction shows the existence of the staggered strong intermolecular C-H…O （DA） hydrogen bonds between adjacent molecules, the intermo- lecular C-H…π hydrogen bonds and the weak π…π stacking interactions, leading to the formation of multi-dimensional supramolecular network based on the Z-mode conformation of the title compound.

Effect of Hyperconjugation on Photovoltaic Performance in Pseduo-2D Perylene Diimide Derivatives

Theπ-πinteraction is acknowledged as the predominant factor to determine the molecular packing in organic photovoltaic materials,while other non-covalent intermolecular interactions especially theσ-πhyperconjugation are often ignored.Herein,a perylene diimide(PDI)derivative named FIDT-PDI is designed and synthesized to shed light into the effect of hyperconjugation on the molecular packing and further the photovoltaic performance.Dynamic NMR and 2D NOE NMR demonstrate the formation of intermolecularσ-πhyperconjugation between the C—H bond of the PDI moiety in one molecule and the phenyl sidechain in another molecule of FIDT-PDI.Benefiting from theσ-πhyperconjugation,FIDT-PDI with twisted backbone reversely exhibits more ordered packing and stronger crystallinity compared with another PDI derivative FIDTT-PDI which has better planarity,consequently achieving superior PCE and higher carrier mobility.This contribution is the first paradigm to unravel the structure-property relationship betweenσ-πhyper-conjugation of conjugated materials and corresponding photovoltaic performance.

Enhancing the deep-red/near-infrared fluorescence of higher rylene diimides via the chalcogen-annulation strategy

Deep-red/near-infrared fluorescence is highly suitable for bioimaging owing to its ability to deeply penetrate tissues,organs,and live animals.However,developing organic fluorophores with high deep-red/near-infrared fluorescence quantum yield(Φ_(FL))and fluorescent brightness remain a significant challenge owing to the energy gap law.Herein,we developed a straightforward and effective chalcogen-annulation strategy by introducing O,S and Se into the bay region of TDI and QDI fluorophores,realizing the increase ofΦFLand fluorescent brightness up to 10 times.To our best knowledge,this study potentially stands as the pioneering instance showcasing the anti-heavy-atom effect of chalcogens,and the absoluteΦFL(93%)and fluorescent brightness(128,200 cm^(-1)mol^(-1)L)of Se-TDI is among top deep-red/near-infrared organic fluorophores currently available.The femtosecond transient absorption(fs-TA)measurements show the absence of obvious changes of the excited state lifetime after the introduction of chalcogens in TDI and QDI fluorophores,indicating that intersystem crossing(ISC)can be neglected in TDI and QDI fluorophores.Theoretical calculations further reveal the chalcogen-annulation strategy increase the radiative rates and reduce the reorganization energy of several accepting modes at the ground state in TDI fluorophores,leading to the suppression of internal conversion(IC)processes.Our chalcogen-annulation strategy,which effectively increases the Φ_(FL)and restricts the IC processes,while remaining unaffected by the heavy-atom effect,offers novel insights and theoretical support for the design and synthesis of deep-red/near-infrared organic fluorophores with high Φ_(FL)and fluorescent brightness.

The marriage of dual-acceptor strategy and C-H activation polymerization:naphthalene diimide-based n-type polymers with adjustable molar mass and decent performance

The development of readily accessible high-mobility n-type semiconducting polymers is in great demand for realizing highperformance p-n junction-based organic electronics.In this study,we demonstrate that with the combination of dual-acceptor strategy and C-H direct arylation polymerization(DAr P),unipolar n-type semiconducting polymers can be conveniently synthesized.By tuning the monomer concentration,three dual-acceptor polymers,namely,poly(naphthalene diimide-alt-dithiophenyl pyrrolopyrrole-dione)(PNDI-DPP),poly(naphthalene diimide-alt-dithiophenyl isoindigo)(PNDI-IID),and poly(naphthalene diimide-alt-dithiophenyl bezothiadiazole)(PNDI-BT)can be obtained via C-H activation with decent number average molecular weight of~10 to 30 kg mol^(-1)and relatively narrow polydispersity index of~2.In addition,these polymers are defect-free in nature as evidenced by the nuclear magnetic resonance.Moreover,we attribute the different molar masses of the three copolymers under the same DAr P condition to the differentα-C-H acidity,which may stem from different electronwithdrawing capability of the hydrogenated acceptor units.Furthermore,the influence of the hydrogenated acceptor monomers on the optical,electrochemical and charge transporting properties is comprehensively studied.Among the three dual-acceptor polymers,PNDI-BT demonstrates the highest electron mobilities of up to 0.6 cm^(2)V^(-1)s^(-1)in unipolar n-type organic transistors because of its relatively planar backbone,larger overlaps of the lowest unoccupied molecular orbital and strong H-aggregation.Note that the transistor performance of PNDI-BT synthesized via C-H activation in this study is at least comparable to the one made by conventional C(sp^(2))-C(sp^(2))Stille or Suzuki cross-coupling polymerization.This study demonstrates the presented protocol can be a useful platform for sustainable and convenient synthesis of high-performance n-type semiconducting polymers.

Highly emissive perylene diimide-based bowtie-shaped metallacycles

Metallacycles hold great promise for fluorescence-based sensing due to their synthetic advantages and unique physicochemical properties. However, it remains highly challenging to develop a versatile methodology for constructing highly emissive metallacycles with targeted functionalities and therefore soughtafter properties. Herein, we report a general strategy to construct a series of highly emissive perylene diimide-based metallacycles via the self-assembly of perylene diimide-based tetrapyridyl ligand with different dicarboxylic ligands featuring fixed angles and cis-Pt(PEt_(3))_(2)(OTf)_(2). Single crystal X-ray diffraction analyses verify the formation of bowtie-like metallacycles with two triangular cavities. Notably, the fluorescence quantum yields of most assemblies exceed 98%, amongst the highest values for metallacycles.Additionally, such metallacycles exhibit sensitive fluorescence responses toward picric acid with a detection limit of 2.8 × 10^(-6)mol/L. This study not only provides a rational strategy for preparing highly emissive bowtie-shaped metallacycles, but also sheds light on their usage in the detection of picric acid and associated compounds.

Interface Engineering of Inverted Perovskite Solar Cells Using a Self-doped Perylene Diimide Ionene Terpolymer as a Thickness-Independent Cathode Interlayer

Inverted perovskite solar cells(PerSCs)are a highly promising candidate in the photovoltaic field due to their low-temperature fabrication process,negligible hysteresis,and easy integration with Si-based solar cells.A cathode interlayer(CIL)is necessary in the development of inverted devices to reduce the trap density and energy barrier between the electron transport layer(ETL)and the electrode.However,most CILs are highly thickness-sensitive due to low conductivity and poor film-forming.In this study,we report on a self-doping perylene imide-based ionene polymer(PNPDIN)used as CIL material to modify electrode in inverted PerSCs.PNPDIN exhibits high conductivity and a good solubility in polar solvent,which results in an improved power conversion efficiency(PCE)from 10.05%(device without a CIL)to 16.97%.When the blend of PNPDIN and Bphen was used as a mixed CIL,the PCE of PerSCs can be further increased to 21.28%owing to the excellent morphology and matched energy level.More importantly,the PCE of the device is highly tolerant to the thickness of the mixed CIL,which benefited from the high conductivity of PNPDIN.This development is expected to provide an excellent mixed CIL material for roll-to-roll processing efficient and stable inverted PerSCs.

Electronic Characteristics of Perylene Diimide Anion Radical and Dianion Films by Quantitative Doping

Due to their unique physicochemical properties,the anion radical and dianion of perylene diimide derivatives(PDIs)recently attracted significant attention for organic semiconductors.However,the impact of packing structure and the radical content for carrier transport in the solid state still need to be determined.Bringing the electron-withdrawing groups is an effective strategy for enablingπ−πstacking distance.Here,bay-tetrachloro-substituted PDI(B-4Cl-PDI)anion radical and dianion films were fabricated quantitatively doped with N_(2)H_(4)·H_(2)O.The radical contents were quantitatively calculated by absorption spectra in different doping ratios.The X-ray powder diffraction patterns showed that the anion radical presented a crystalline structure,and dianion aggregates exhibited an amorphous structure.With precise manipulation of the radical content,the anion radical aggregates and dianion aggregates showed the maximum electrical conductivity value of 0.024 and 0.0018 S/cm,respectively.The experiment results show that doping level and aggregate structure play a crucial role in electronic transport properties.

Sila-annulated terrylene diimides for balanced ambipolar transporting

The key building blocks,tetrachlorinated terrylene diimides and the targeted sila-annulated terrylene diimides(Si-TDIs and 2Si-TDIs)were synthesized for the first time.Single-crystal analysis verified the almost planar molecular configurations of both Si-TDIs and 2Si-TDIs.They exhibited intriguing optical properties including red-shifted absorption and near-infrared emission properties with excellent fluorescence quantum yields,as well as precisely controlled HOMO/LUMO energy levels by Si-heteroannulation.The single-crystal organic field-effect transistors based on 2Si-TDI 5a featuring long and branched alkyl chains demonstrated well-balanced ambipolar transporting properties with electron/hole mobilities of 0.10/0.18 cm2 V^(−1)s^(−1).

Arylene Diimide Derivatives as Anolyte Materials with Two-Electron Storage for Ultrastable Neutral Aqueous Organic Redox Flow Batteries

Two-electron neutral aqueous organic redox flow batteries(AORFBs)hold more promising applications in the power grid than one-electron batteries because of their higher capacity.However,their development is strongly limited by the structural instability of the highly reduced species.By combining the extendedπ-conjugation structure of the anolytes and the enhanced aromaticity of the highly reduced species,we reported a series of highly conjugated and inexpensive arylene diimide derivatives(NDI,PDI,and TPDI)as novel two-electron storage anolyte materials for ultrastable AORFBs.Matched with(ferrocenylmethyl)trimethylammonium chloride(FcNCl)as catholyte,arylene diimide derivative-based AORFBs showed the highest stability in two-electron AORFBs to date.The NDI/FcNCl-based AORFB delivered 98.44%capacity retention at 40 mA cm^(−2)for 350 cycles;TPDI/FcNCl-based AORFB also showed remarkable stability with 97.22%capacity retention at 20 mA cm^(−2)over 200 cycles.This finding lays the theoretical foundation and offers a reference for improving the stability of two-electron AORFBs.

Rylene Diimide and Dithienocyanovinylene Copolymers for Polymer Solar Cells

Two polymers containing （E）-2,3-bis（thiophen-2-yl）acrylonitrile （CNTVT） as a donor unit, perylene diimide （PDI） or naphthalene diimide （NDI） as an acceptor unit, are synthesized by the Stille coupling copolymerization, and used as the electron acceptors in the solution-processed organic solar cells （OSCs）. Both polymers exhibit broad absorption in the region of 300-850 nm. The LUMO energy levels of the resulted polymers are ca. -3.93 eV and the HOMO energy levels are -5.97 and -5.83 eV. In the binary blend OSCs with PTB7-Th as a donor, PDI polymer yields the power conversion efficiency （PCE） of up to 1.74%, while NDI polymer yields PCE of up to 3.80%.

A new perylene diimide-based colorimetric and fluorescent sensor for selective detection of Cu^(2+) cation

A new perylene diimide (PDI) ligand (1) functionalized with a dipicolylethylenediamine (DPEN) moiety was synthesized and first used as a colorimetric and fluorometric dual-channel sensor to specifically detect the presence of Cu2+ over a wide range of other cations. The solution of 1 (10 μmol/L) upon ad-dition of Cu2+ displayed distinguishing pink color compared with other cations including K+,Ni2+,Ca2+,Mn2+,Na+,Sr2+,Zn2+,Co2+,Cd2+,Mg2+,Cr3+,Ag+,and Ba2+,indicating the sensitivity and selectivity of 1 to Cu2+. Thus,the advantage of this assay is that naked-eye detection of Cu2+ becomes possible. More-over,among these metal ions investigated,only Cu2+ quenched more than half fluorescent intensity of 1. The ESI-TOF spectrum of a mixture of 1 and CuCl2 in combination of the fluorescence titration spectra of 1 (10 μmol/L) upon addition of various amounts of Cu2+ revealed the formation of a 2︰1 metal-ligand complex through the metal coordination interaction.

Perylene Diimide Based Isomeric Conjugated Polymers as Efficient Electron Acceptors for All-polymer Solar Cells

We present here a series of perylene diimide(PDI)based isomeric conjugated polymers for the application as efficient electron acceptors in all-polymer solar cells(all-PSCs).By copolymerizing PDI monomers with 1,4-diethynylbenzene(para-linkage)and 1,3-diethynylbenzene(meta-linkage),isomeric PDI based conjugated polymers with parallel and non-parallel PDI units inside backbones were obtained.It was found that para-linked conjugated polymer(PA)showed better solubility,strongerπ-πstacking,more favorable blend morphology,and better photovoltaic performance than those of meta-linked conjugated polymers(PM)did.Device based on PTB7-Th:PA(PTB7-Th:poly{4,8-bis[5-(2-ethylhexyl)-thiophen-2-yl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)-carbonyl]thieno[3,4-b]thiophene-4,6-diyl})showed significantly enhanced photovoltaic performance than that of PTB7-Th:MA(3.29%versus 0.92%).Moreover,the photovoltaic performance of these polymeric acceptors could be further improved via a terpolymeric strategy.By copolymerizing a small amount of meta-linkages into PA,the optimized terpolymeric acceptors enabled to enhance photovoltaic performance with improved the short-circuit current density(Jsc)and fill factor(FF),resulting in an improved power conversion efficiency(PCE)of 4.03%.

Photoinduced excimer generation in perylene diimide dimer:effects of solvent polarity[Invited]

The aggregation and photoinduced excited state dynamics of organic π-conjugated molecules play a vital role in solar energy conversion and applications.This work investigates how solvent polarity affects the aggregation behavior and the photophysical process of perylene diimide dimer(PDI-II).The results show that the conjugations between PDI intramolecular chromophores are more likely to generate excimer,and the conjugations between PDI intermolecular chromophores are more likely to experience symmetry-breaking charge separation.Our study can provide a reference for the design of high-efficiency solar energy conversion materials.

A Red-Emissive Sextuple Hydrogen-Bonding Self-Assembly Molecular Duplex Bearing Perylene Diimide Fluorophores for Warm-White Organic Light-Emitting Diode Application

A novel sextuple hydrogen-bonding （HB） self-assembly molecular duplex bearing red-emitting perylene diimide （PDI） fluorophores, namely PDIHB, was synthesized, and its molecular structure was confirmed by IH NMR, 13C NMR, TOF-MS and 2D NMR. Compared with the small molecular reference compound PDI, PDIItB shows one time enhanced fluorescence efficiency in solid state （4.1% vs. 2.1%）. More importantly, the presence of bulky HB oli- goamide strands in PDIHB could trigger effective spatial separation between guest and host fluorophores in thin solid film state, hence inefficient energy transfer occurs between the blue-emitting host 2TPhNII/B and red guest PDIHB in the 2 wt% guest/host blending film. As a result, a solution-processed organic light-emitting diode （OLED） with quite simple device structure of ITO/PEDOT：PSS （40 nm）/PVK （40 nm）/PDIHB （2 wt%）： 2TPhNII-IB （50 nm）/LiF （0.8 nm）/A1 （100 nm） could emit bias-independent warm-white electroluminescence with stable Commission Intemationale de L＇Eclairage coordinates of （0.42, 0.33）, and the maximum brightness and current efficiency of this device are 260 cdom-2 and 0.49 cd·A-1, respectively. All these results indicated that HB self-assembly supramolecular fluorophores could act as prospective materials for white OLED application.