Donor-acceptor Arrays Research Articles

Efficient Charge Transfer Driven Electrochemiluminescence in Heteroatom-Involved Cocrystal Engineering for Detection of Uranyl Ions.

Embracing strategies that circumvent the complexities and disordered structures of electrochemiluminescence (ECL) emitters to improve charge transfer efficiency is crucial for advancing ECL technology to the forefront. Here, heteroatom-involved cocrystal engineering was introduced, constructing an ECL system with controllability of the charge transfer process. Through the mutual recognition and coassembly between functional monomers, highly ordered cocrystal superstructures are formed. The layered donor-acceptor arrays in cocrystals accelerated charge transfer, producing a remarkable ECL performance. Furthermore, distinct heteroatoms possess the capability to modulate the charge distribution of monomers by either pushing or pulling electrons. This modulation ultimately affects the charge transfer pathways within cocrystals, enabling ECL emissions of varying intensities and wavelengths. Notably, the presence of UO22+ would significantly inhibit the charge transfer in cocrystals, causing a quenching of ECL signal. This unique characteristic enables precise and selective detection of UO22+. The heteroatom-involved cocrystals hold immense potential to construct next-generation ECL emitters and create fresh opportunities for the advancement of ECL technology.

Lamellarly Segregated Columnar Liquid Crystalline Alternating Copolymers with High Ambipolar Charge Mobilities

Segregated assembly in a π-conjugated donor–acceptor molecular system is imperative to create heterojunctions for optoelectronic applications. Here, we report lamellarly segregated columnar donor–acceptor arrays based on liquid crystalline alternating copolymers to afford high ambipolar and balanced charge mobilities. Especially, the rational molecular design renders the formation of a highly ordered hexagonal columnar superlattice based on the alternate lamellar structures. The ideal lamellar columnar heterojunction with regular distribution of donor–acceptor columns and remarkable intracolumnar order enables highly efficient and balanced hole and electron mobilities of 0.68 and 3.60 cm2 V–1 s–1, respectively. This work demonstrates the unique self-organization process of alternating copolymers containing two electronically active constituents and provides new insights into the design of ambipolar semiconducting soft materials for electronic and photovoltaic applications.

Controlling Electronic Events Through Rational Structural Design in Subphthalocyanine-Corrole Dyads: Synthesis, Characterization, and Photophysical Properties.

Porphyrinoids are considered perfect candidates for their incorporation into electron donor-acceptor (D-A) arrays due to their remarkable optoelectronic properties and low reorganization energies. For the first time, a series of subphthalocyanine (SubPc) and corrole (Cor) were covalently connected through a short-range linkage. SubPc axial substitution strategies were employed, which allowed the synthesis of the target molecules in decent yields. In this context, a qualitative synthetic approach was performed to reverse the expected direction of the different electronic events. Consequently, in-depth absorption, fluorescence, and electrochemical assays enabled the study of electronic and photophysical properties. Charge separation was observed in cases of electron-donating Cors, whereas a quantitative energy transfer from the Cor to the SubPc was detected in the case of electron accepting Cors.

Photoactive Organic/Inorganic Hybrid Materials with Nanosegregated Donor–Acceptor Arrays

AbstractThe synthesis of the first mesogenic donor‐acceptor polyoxometalate (POM)‐based hybrid is herein described. The structural and electronic properties of the hybrid compound were evaluated through combination of small‐ and wide‐angle X‐ray scattering, optical microscopy, electrochemistry and photoluminescence. In the solid state, the compound behaves as a birefringent solid, displaying a lamellar organization in which double‐layers of POMs and bis(thiophene)thienothiophene organic donors alternate regularly. Noticeably, the sub‐unit organizations in the composite are similar to that observed for the individual POM and organic donor precursors. Photophysical studies show that in the hybrid, the fluorescence of the organic donor unit is considerably quenched both in solution and in the solid state, which is attributed to occurrence of intramolecular charge‐separated state.

Photoactive Organic/Inorganic Hybrid Materials with Nanosegregated Donor-Acceptor Arrays.

The synthesis of the first mesogenic donor-acceptor polyoxometalate (POM)-based hybrid is herein described. The structural and electronic properties of the hybrid compound were evaluated through combination of small- and wide-angle X-ray scattering, optical microscopy, electrochemistry and photoluminescence. In the solid state, the compound behaves as a birefringent solid, displaying a lamellar organization in which double-layers of POMs and bis(thiophene)thienothiophene organic donors alternate regularly. Noticeably, the sub-unit organizations in the composite are similar to that observed for the individual POM and organic donor precursors. Photophysical studies show that in the hybrid, the fluorescence of the organic donor unit is considerably quenched both in solution and in the solid state, which is attributed to occurrence of intramolecular charge-separated state.

Difluoroborate-based conjugated organic polymer: a high-performance heterogeneous photocatalyst for oxidative coupling reactions

A photoactive difluoroborate-based conjugated organic polymer (B-COP) with A3B2-type donor–acceptor arrays in the polymer framework was synthesized by direct polycondensation and exhibited amorphous structure, high thermal and photophysical stability. The B-COP was shown to be a highly efficient heterogeneous photocatalyst for a wide range of photocatalytic transformations, including the oxidative coupling of primary amine and cross-dehydrogenative coupling reactions between tetrahydroisoquinolines and nucleophiles such as nitromethane, nitroethane, acetone and phenylethyl ketone.

Hydrogen-Bonded Donor-Acceptor Arrays at the Solution-Graphite Interface.

Controlling the nanoscale morphology of organic thin films represents a critical challenge in the fabrication of organic (opto)electronic devices. The morphology of the (multicomponent) thin films in turn depends on the mutual orientation of the molecular components and their supramolecular packing on the surface. Here, it is shown how the surface co-assembly of electron-donating and -accepting building blocks can be controlled via (supra)molecular design. Hexa-peri-hexabenzocoronene (HBC) derivatives with multiple hydrogen-bonding (H-bonding) sites were synthesized and their co-assembly with alkyl-substituted perylene tetracarboxy diimide (PDI) was studied using scanning tunneling microscopy (STM) at the solution-graphite interface. STM data shows that electron-rich HBCs co-assemble laterally with electron deficient PDIs via preprogrammed H-bonding sites with high fidelity. The surface stoichiometry of the two components could be readily tuned by changing the number of H-bonding sites on the HBC derivatives via organic synthesis. This model study highlights the utility of (supra)molecular design in co-assembly of building blocks relevant for organic electronics.

Effective photocurrent generation in supramolecular porphyrin-fullerene conjugates assembled by crown ether-alkyl ammonium cation interactions

In this paper, a new approach for fabricating donor-acceptor (D-A) arrays, (Si-TCP)n-PhC60NH3+, 5,10,15,20-Tetrakis(benzo-15-crown-5)porphyrin (TCP), 2-Phenyl-5-(n-butylammonium)-3,4-fulleropyrrolidine (PhC60NH3+), on indium-tin oxide (ITO) electrode is demonstrated. Electronic absorption spectra, atomic force microscopy, infrared spectroscopy, electrochemical impedance spectroscopy, and X-ray diffraction analysis were used as powerful tools to characterize (Si-TCP)n arrays and (Si-TCP)n-PhC60NH3+ arrays on the ITO electrode. The (Si-TCP)n-PhC60NH3+ arrays was immobilized on the electrode avoided the traditional fussy operations for immobilizing both porphyrin materials and fullerene, which led to a significantly reduction of background signal and an enhancement of initial photocurrent signal. These results would provide fundamental clues for the molecular design of high-performance organic photovoltaics.

Aminoglutethimide-imprinted xerogels in bulk and spherical formats, based on a multifunctional organo-alkoxysilane precursor

The multifunctional alkoxysilane precursor, 2,6-bis(propyl-trimethoxysilylurelene)pyridine (DPS) was designed and synthesized, envisaging a multiple hydrogen-bond interaction in the molecular imprinting of the drug aminoglutethimide (AGT). Imprinted xerogels were obtained in bulk and spherical formats. The spherical format was achieved by pore-filling onto spherical mesoporous silica, as a straightforward technique to generate the spherical format. The bulk gels presented better selectivity for the template against its glutarimide (GLU) analogue (selectivity factor: bulk 13.4; spherical 4.6), and good capacity (bulk 5521μmol/L; spherical 2679μmol/L) and imprinting factor parameters (bulk 11.3; spherical 1.4). On the other hand, the microspherical format exhibited better dynamic properties associated to chromatographic efficiency (theoretical plates: bulk 6.8; spherical 75) and mass transfer, due mainly to the existence of a mesoporous network, lacking in the bulk material. The performance of the imprinted xerogels was not as remarkable as that of their acrylic counterparts, previously described. Overall it was demonstrated that the use of designed new “breeds” of organo-alkoxysilanes may be a strategy to achieve satisfactory imprints by the sol–gel processes. DPS may in principle be applied even more effectively to other templates bearing better-matching spatially compatible acceptor–donor–acceptor arrays.

Photon upconversion in supramolecular gel matrixes: spontaneous accumulation of light-harvesting donor-acceptor arrays in nanofibers and acquired air stability.

Efficient triplet-triplet annihilation (TTA)-based photon upconversion (UC) is achieved in supramolecular organogel matrixes. Intense UC emission was observed from donor (sensitizer)-acceptor (emitter) pairs in organogels even under air-saturated condition, which solved a major problem: deactivation of excited triplet states and TTA-UC by molecular oxygen. These unique TTA-UC molecular systems were formed by spontaneous accumulation of donor and acceptor molecules in the gel nanofibers which are stabilized by developed hydrogen bond networks. These molecules preorganized in nanofibers showed efficient transfer and migration of triplet energy, as revealed by a series of spectroscopic, microscopic, and rheological characterizations. Surprisingly, the donor and acceptor molecules incorporated in nanofibers are significantly protected from the quenching action of dissolved molecular oxygen, indicating very low solubility of oxygen to nanofibers. In addition, efficient TTA-UC is achieved even under excitation power lower than the solar irradiance. These observations clearly unveil the adaptive feature of host gel nanofiber networks that allows efficient and cooperative inclusion of donor-acceptor molecules while maintaining their structural integrity. As evidence, thermally induced reversible assembly/disassembly of supramolecular gel networks lead to reversible modulation of the UC emission intensity. Moreover, the air-stable TTA-UC in supramolecular gel nanofibers was generally observed for a wide combination of donor-acceptor pairs which enabled near IR-to-yellow, red-to-cyan, green-to-blue, and blue-to-UV wavelength conversions. These findings provide a new perspective of air-stable TTA-UC molecular systems; spontaneous and adaptive accumulation of donor and acceptor molecules in oxygen-blocking, self-assembled nanomatrixes. The oxygen-barrier property of l-glutamate-derived organogel nanofibers has been unveiled for the first time, which could find many applications in stabilizing air-sensitive species in aerated systems.

An enhanced photoelectrochemical immunosensing platform: Supramolecular donor–acceptor arrays by assembly of porphyrin and C60

A novel self-assemble approach was developed for constructing a linear bicontinuous donor–acceptor, (H2BCPP)n–C60, arrays on indium-tin oxide electrode. Electronic absorption spectra, fluorescence spectra and atomic force microscopy were used as powerful tools to characterize H2BCPP, (H2BCPP)n arrays and (H2BCPP)n–C60 arrays. The (H2BCPP)n–C60 arrays enhanced the photocurrent generation capability, and presented an efficient photoelectrochemical immunosensing platform for the ultrasensitive detection of carcinoembryonic antigen (CEA). The quantitative measurement of CEA was based on the decrease in the photocurrent intensity of the (H2BCPP)n–C60 arrays, which was resulted from the competition between CEA and CEA-CdTe. A linear relationship between the photocurrent decrease and the CEA concentration was obtained in the wide range from 0.01 to 60ngmL−1 with a detection limit of 3.4pgmL−1. The proposed sensor showed high sensitivity, stability and reproducibility, and provided a promising platform for other biomolecular detection.

Alternating donor-acceptor arrays from hexa-peri-hexabenzocoronene and benzothiadiazole: synthesis, optical properties, and self-assembly.

Donor-acceptor (D-A) structures were obtained by alternating arrays of hexa-peri-hexabenzocoronene (HBC) and benzo[c][1,2,5]thiadiazole (BTZ). Optoelectronic investigations revealed a charge transfer due to strong push-pull interactions. 2 D wide-angle X-ray scattering (WAXS) data indicated an arrangement in liquid-crystalline columnar assemblies, in which the π-stacking distances and molecular orientation depend on the number of HBC units in the molecules.

Side-Chain Supramolecular Polymers Employing Conformer Independent Triple Hydrogen Bonding Arrays

Derivatives of thymine have been extensively used to promote supramolecular materials assembly. Such derivatives can be synthetically challenging to access and may be susceptible to degradation. The current article uses a conformer-independent acceptor–donor–acceptor array (ureidopyrimidine) which forms moderate affinity interactions with diamidopyridine derivatives to effect supramolecular blend formation between polystyrene and poly(methyl methacrylate) polymers obtained by RAFT which have been functionalized with the hydrogen bonding motifs.

A π‐Stacked Porphyrin–Fullerene Electron Donor–Acceptor Conjugate That Features a Surprising Frozen Geometry

A "frozen" electron donor-acceptor array that bears porphyrin and fullerene units covalently linked through the ortho position of a phenyl ring and the nitrogen of a pyrrolidine ring, respectively, is reported. Electrochemical and photophysical features suggest that the chosen linkage supports both through-space and through-bond interactions. In particular, it has been found that the porphyrin singlet excited state decays within a few picoseconds by means of a photoinduced electron transfer to give the rapid formation of a long-lived charge-separated state. Density functional theory (DFT) calculations show HOMO and LUMO to be localized on the electron-donating porphyrin and the electron-accepting fullerene moiety, respectively, at this level of theory. More specifically, semiempirical molecular orbital (MO) configuration interaction (CI) and unrestricted natural orbital (UNO)-CI methods shed light on the nature of the charge-transfer states and emphasize the importance of the close proximity of donor and acceptor for effective electron transfer.

ChemInform Abstract: Introduction of Two Anthracene Moieties into Perylenebis(dicarboximide) Core by Suzuki—Miyaura Coupling Toward Construction of Donor—Acceptor Arrays.

AbstractThe optical and electrochemical properties of the new stable and colored compounds (IV) and (V) are investigated in CHCl3 and in CH2Cl2, respectively.

Targeting π‐Conjugated Multiple Donor–Acceptor Motifs Exemplified by Tetrathiafulvalene‐Linked Quinoxalines and Tetrabenz[bc,ef,hi,uv]ovalenes: Synthesis, Spectroscopic, Electrochemical, and Theoretical Characterization

An efficient synthetic approach to a symmetrically functionalized tetrathiafulvalene (TTF) derivative with two diamine moieties, 2-[5,6-diamino-4,7-bis(4-pentylphenoxy)-1,3-benzodithiol-2-ylidene]-4,7-bis(4-pentylphenoxy)-1,3-benzodithiole-5,6-diamine (2), is reported. The subsequent Schiff-base reactions of 2 afford large π-conjugated multiple donor-acceptor (D-A) arrays, for example, the triad 2-[4,9-bis(4-pentylphenoxy)-1,3-dithiolo[4,5-g]quinoxalin-2-ylidene]-4,9-bis(4-pentylphenoxy)-1,3-dithiolo[4,5-g]quinoxaline (8) and the corresponding tetrabenz[bc,ef,hi,uv]ovalene-fused pentad 1, in good yields and high purity. The novel redox-active nanographene 1 is so far the largest known TTF-functionalized polycyclic aromatic hydrocarbon (PAH) with a well-resolved (1)H NMR spectrum. The electrochemically highly amphoteric pentad 1 and triad 8 exhibit various electronically excited charge-transfer states in different oxidation states, thus leading to intense optical intramolecular charge-transfer (ICT) absorbances over a wide spectral range. The chemical and electrochemical oxidations of 1 result in an unprecedented TTF(⋅+) radical cation dimerization, thereby leading to the formation of [1(⋅+)](2) at room temperature in solution due to the stabilizing effect, which arises from strong π-π interactions. Moreover, ICT fluorescence is observed with large solvent-dependent Stokes shifts and quantum efficiencies of 0.05 for 1 and 0.035 for 8 in dichloromethane.

Synthesis and photoinduced electron transfer characteristic of a bis (zinc porphyrin)‐perylene bisimide array

In this article, a donor–acceptor array consisting of two zinc porphyrin (ZnPOR) units attached to the 1,7‐positions of perylene‐3,4:9,10‐bis(dicarboximide) (PDI) was synthesized and characterized. This double‐wing molecule exhibits very broad absorption in the region from 300 to 900 nm. Especially, its lower energy absorption feature presumably arises from donor–acceptor interactions. The fluorescence emission spectra confirmed that photoinduced electron transfer occurred from POR to perylene bisimide moiety in this triad. In contrast to previously studied systems incorporating POR and PDI groups, this array shows the evidence of a relatively strong ground‐state electronic coupling between the donor and acceptor moieties. Additionally, highest occupied molecular orbital and lowest unoccupied molecular orbital values of the array were acquired by cyclic voltammetry (CV). The results showed that these energy values fulfill the energetic conditions required for the proposed electron transfer. More importantly, the photocurrent measurement showed that this molecule exhibits a high capacity to form a photoinduced charge‐separated state and to produce steady and prompt cathodic photocurrent responses. These results confirmed the role of this new array toward harvesting light energy and generating photocurrent during the operation of a photoelectrochemical cell. Copyright © 2011 John Wiley & Sons, Ltd.

Highly Efficient Photoinduced Electron Transfer in a Novel Tetrakis(tetraphenylporphyrinatozinc)/Perylenetetracarboxidiimide Array and Its Application to a Photovoltaic Device

Abstract A novel donor–acceptor array consisting of four 5-(p-substituted phenyl)-10,15,20-triphenylporphyrinatozinc (POR) complexes attached to the 1,6,7,12-positions of perylene-3,4:9,10-tetracarboxidiimide (PDI) was synthesized and characterized. HOMO and LUMO values of the array were aquired by cyclic voltammetry. Photophysical properties were studied by steady-state UV–vis and fluorescence spectroscopy. The results showed that this compound absorbs strongly from 300 to 700 nm, making it an ideal system to harvest polychromatic light. After selective excitation of the POR moiety or PDI moiety, an almost complete fluorescence quenching was observed, indicating that highly efficient photoinduced electron transfer occurs in this array. The predominant quenching process for PDI–POR4 array is electron-transfer yielding POR4+–PDI−. The self-assemblies of this molecular in polar and nonpolar solvents were investigated. Intermolecular π–π interaction in cooperation with the van der Waals interaction between POR and PDI component leads to the formation of spherical nanoparticles and ribbon-like morphological structures in methanol and n-hexane, respectively. Photoelectrochemical studies exhibited prompt and steady photocurrent photovoltage response. Moreover, photovoltaic measurement on this array reveals efficient light energy conversion properties, such as a fill factor of 0.42. These results are of particular relevance for photovoltaic nanodevices and solar energy conversion applications.

Self-Assembly of a Water-Soluble Tricyclic Heterocycle into J-Type Rosette Nanotubes

ABSTRACTThe synthesis and self-assembly of a water-soluble, tricyclic, self-complementary heterocycle that features the hydrogen bond donor-acceptor arrays of both guanine (G) and cytosine (C) juxtaposed between a pyridine ring is presented. In solution, this tricycle, which has been termed xK1, self-assembles into Rosette Nanotubes (RNTs) that have an inner diameter of 1.4 nm. Unlike the RNTs formed from the bicyclic congener K1, we demonstrate that xK1 with its extended ð system, forms a J-type RNT assembly determined through UV-Vis, CD and fluorescence spectroscopy experiments. This observation brings the possibility of developing electrically conducting RNTs for applications in the areas of photovoltaics and molecular wires.

Control over Charge Transfer through Molecular Wires by Temperature and Chemical Structure Modifications

A series of electron donor-acceptor arrays containing π-conjugated oligofluorenes (oFL) of variable length between a zinc porphyrin (ZnP) as electron donor and fullerene (C(60)) as electron acceptor have been prepared by following a convergent synthesis. The electronic interactions between the electroactive species were determined by cyclic voltammetry, UV-visible, fluorescence, and femto/nanosecond transient absorption spectroscopy. Our studies clearly confirm that, although the C(60) units are connected to the ZnP donor through π-conjugated oFL frameworks, no significant electronic interactions prevail in the ground state. Theoretical calculations predict that a long-range electron transfer occurs primarily due to a maximized π-conjugated pathway from the donor to the acceptor. Photoexcitation of ZnP-oFL(n)-C(60) results in transient absorption maxima at 715 and 1010 nm, which are unambiguously attributed to the photolytically generated radical ion pair state, [ZnP(•+)-oFL(n)-C(60)(•-)], with lifetimes in the microsecond time regime. Temperature-dependent photophysical experiments have shown that the charge-transfer mechanism is controllable by temperature. Both charge separation and charge recombination processes give rise to a molecular wire behavior of the oFL moiety with an attenuation factor (β) of 0.097 Å(-1). The correlation β to the connection pattern between the ZnP donor and the oFL linker revealed that even small alterations of the linker π-electron system break the homogeneous π-conjugation pattern, leading to higher values of β.