Encoding Hole-Particle Information in the Multi-Channel MolOrbImage for Machine-Learned Excited-State Energies of Large Photofunctional Materials.

We present a novel class of one-electron multi-channel molecular orbital images (MolOrbImages) designed for the prediction of excited-state energetics in conjunction with the state-of-the-art VGG-type machine-learning architecture. By representing hole and particle states in the excitation process as channels of MolOrbImages, the revised VGG model achieves excellent prediction accuracy for both low-lying singlet and triplet states, with mean absolute errors (MAEs) of <0.08 and <0.1 eV for QM9 molecules and large photofunctional materials with up to 560 atoms, respectively. Remarkably, the model demonstrates exceptional performance (MAE < 1 kcal/mol) for the T1 state of QM9 molecules, making it a non-system-specific model that approaches chemical accuracy. The general rules attained, for instance, the improved performance with well-defined MO energies and the reduced overfitting concern via the inclusion of physically insightful hole-particle information, provide invaluable guidelines for the further design of orbital-based descriptors targeting molecular excited states.

Photo- and Temperature-Induced Reversible Structural Transformation between Dodecanuclear and Pentadecanuclear Gold(I) Sulfido Complexes.

Stimuli-responsive structural transformation has attracted much attention for its potential to mimic the behavior of biological transformations and functions. Here, two unprecedented dodecanuclear and pentadecanuclear gold(I) sulfido clusters (denoted trans-Au12 and trans-Au15, respectively) with impressive stimuli-responsive interconversion have been obtained by taking advantage of the judiciously designed tridentate phosphine ligand Ltrans as the building block. Both UV light and temperature can be applied to trigger the structural conversions between trans-Au12 and trans-Au15. In addition, NMR, high-resolution electrospray ionization mass spectrometry, and UV-vis absorption spectroscopy have been employed to monitor the transformation process and decipher the mechanism of structural conversion. This work not only provides a paradigm to investigate photo-induced cluster-to-cluster transformation based on polydentate phosphine ligands but also offers a new direction for the construction of the stimuli-responsive materials.

Thermally Stimulated Delayed Phosphorescence (TSDP)-Based Gold(III) Complexes of Tridentate Pyrazine-Containing Pincer Ligand with Wide Emission Color Tunability and Their Application in Organic Light-Emitting Devices.

A new class of pyrazine-based carbazole-containing gold(III) complexes featuring thermally stimulated delayed phosphorescence (TSDP) properties has been designed and synthesized. The emission colors are found to be sensitive to the coordinating atom of the carbazolyl ligands at the gold(III) center, with emission energies spanning from green to red. The efficiency of TSDP can be enhanced by lowering the polarity of the solvent, as supported by the variable-temperature emission and computational studies. Interestingly, a significant spectral shift in electroluminescence with the change of Commission Internationale de L'Eclairage (CIE) coordinates from (0.35, 0.60) to (0.44, 0.54) has been achieved by simply changing the host material from CBP to TmPyPB. Solution-processable organic light-emitting devices (OLEDs) have also been fabricated, with maximum current efficiencies of up to 22.4 cd A-1 and maximum external quantum efficiencies (EQEs) approaching 7.0%. A higher current efficiency of 35.1 cd A-1 and EQE of 10.7% can be achieved for the vacuum-deposited device based on 1, representing the first demonstration of pyrazine-based tridentate ligand-containing gold(III) complexes as phosphorescent material for OLED application.

Realization of Thermally Stimulated Delayed Phosphorescence in Arylgold(III) Complexes and Efficient Gold(III) Based Blue-Emitting Organic Light-Emitting Devices.

To address and overcome the difficulties associated with the increased reactivity and susceptibility of blue emitters to deactivation pathways arising from the high-lying triplet excited states, we have successfully demonstrated an innovative strategy of harvesting triplet emission via the "thermally stimulated delayed phosphorescence" mechanism, where thermal up-conversion of excitons from the lower-energy triplet excited states (T1) to higher-energy triplet excited states (T1') are observed to generate blue emission. The lower-lying T1 excited state could serve as a mediator to populate the emissive T1' state by up-conversion via reverse internal conversion, which could enhance the photoluminescence quantum yield by over 20-folds. Organic light-emitting devices with respectable external quantum efficiencies of up to 7.7% and sky-blue emission with CIE coordinates of (0.17, 0.37) have been realized. The operational stability for the device based on complex 1 has also been explored, and the device is found to show fairly respectable lifetime. This work opens up a new avenue to the design and synthesis of blue phosphorescent emitters.

Design of a water-soluble hybrid nanocomposite of CdTe quantum dots and an iridium complex for photoinduced charge transfer.

We report the use of an organo-iridium dye conjugated with a water-soluble copolyethylenimine polymer, allowing the hybrid material to be used in combination with thioacid-coated CdTe quantum dots in an aqueous medium. When they are combined, hot carrier cooling observed in the pure quantum-dot case is heavily suppressed indicating fast (ps) electron transfer on a timescale that competes with non-radiative (Auger) relaxation.

Rational molecular design for realizing high performance sky-blue-emitting gold(iii) complexes with monoaryl auxiliary ligands and their applications for both solution-processable and vacuum-deposited organic light-emitting devices.

A new class of sky-blue-emitting arylgold(iii) complexes containing tridentate bis-cyclometalating ligands derived from 2,6-diphenylpyridine (C^N^C) has been successfully designed and synthesized. By systematically varying the electron-withdrawing groups from cyano, fluoro, and trifluoromethyl to trifluoromethoxy groups on the phenyl ring of the tridentate C^N^C ligands, the emission maxima of these complexes have been significantly blue-shifted from 492 nm to 466 nm in dichloromethane solution. In addition, the higher excited state distortion with respect to the ground state associated with the multiple fluoro substitutions at the tridentate ligand has been successfully reduced by the employment of trifluoromethyl and trifluoromethoxy groups, as revealed by the Huang-Rhys factor. Taking advantage of their high photoluminescence quantum yields of up to 43% in the solid-state MCP thin-films, high performance solution-processable and vacuum-deposited organic light-emitting devices with external quantum efficiencies of up to 5.3% and 11.3%, respectively, have been realized. This work represents the first demonstration of sky-blue-emitting gold(iii) complexes with an x chromaticity coordinate of <0.2.

Photochromic oligothienoacene derivatives with photo-switchable luminescence properties and computational studies.

Photochromic thieno[3,2-b]thiophenes and dithieno[3,2-b:2',3'-d]thiophene with photo-switchable luminescence properties have been synthesized using a Suzuki cross-coupling reaction; their electronic structures, and photochromic and luminescence behaviour have also been studied.

Covalent and Non-covalent Conjugation of Few-Layered Graphene Oxide and Ruthenium(II) Complex Hybrids and Their Energy Transfer Modulation via Enzymatic Hydrolysis.

Pyrene-containing ruthenium(II) tris-bipyridine complexes have been prepared. These complexes have been non-covalently attached onto the few-layered graphene oxide (GO) sheets through their high binding affinity for flat π-surfaces. Alternatively, the reduced graphene oxide (rGO) sheets have also been covalently functionalized with the ruthenium(II) tris-bipyridine complex. The prepared conjugates have been characterized by transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy, thermogravimetric analysis (TGA), and UV-visible absorption spectroscopy. The energy transfer properties of the resulted conjugates between the graphene and transition metal complexes have been studied via esterase hydrolysis. The energy transfer efficiencies were found to vary with the separation between the donor and the acceptor units.

Parallel folding topology-selective label-free detection and monitoring of conformational and topological changes of different G-quadruplex DNAs by emission spectral changes via FRET of mPPE-Ala-Pt(ii) complex ensemble.

The formation of supramolecular assemblies between [Pt(bzimpy-Et){C[triple bond, length as m-dash]CC6H4(CH2NMe3-4)}]Cl2 (1) and mPPE-Ala and the FRET properties of the ensemble have been revealed from the UV-vis absorption, steady-state emission and time-resolved emission decay studies. The two-component mPPE-Ala-1 ensemble has been employed in a "proof-of-principle" concept for label-free detection of G-quadruplex DNAs with the intramolecular propeller parallel folding topology, such as c-myc, in aqueous buffer solution. By the modulation of the aggregation/deaggregation of the polymer-metal complex aggregates and hence the FRET from the mPPE-Ala donor to the aggregated 1 as acceptor, the ensemble has been demonstrated for sensitive and selective label-free detection of c-myc via the monitoring of emission spectral changes of the ensemble. Ratiometric emission of the ensemble at 461 and 662 nm has been shown to distinguish the intramolecular propeller parallel G-quadruplex folding topology of c-myc from other G-quadruplex-forming sequences of different folding topologies, owing to the strong and specific interactions between c-myc and 1 as suggested by the UV-vis absorption and UV melting studies. In addition, the formation of high-order intermolecular multimeric G-quadruplexes from c-myc under molecular crowding conditions has been successfully probed by the ratiometric emission of the ensemble. The conformational and topological transition of human telomeric DNA from the mixed-hybrid form to the intramolecular propeller parallel form, as observed from the circular dichroism spectroscopy, has also been monitored by the ratiometric emission of the ensemble. The ability of the ensemble to detect these conformational and topological transitions of G-quadruplex DNAs has been rationalized by the excellent selectivity and sensitivity of the ensemble towards the intramolecular propeller parallel G-quadruplex DNAs and their high-order intermolecular multimers, which are due to the extra stabilization gained from Pt···Pt and π-π interactions in addition to the electrostatic and hydrophobic interactions found in the polymer-metal complex aggregates.

Proof of Potassium Ions by Luminescence Signaling Based on Weak Gold-Gold Interactions in Dinuclear Gold(I) Complexes.

Two versatile luminescence ion probes for potassium ions have been designed based on the "switching on and off" of the gold-gold interaction. Addition of potassium ions to the gold(I) complexes [Au2 (R2 PCH2 PR2 )(S-benzo[15]crown-5)2 ] (see the picture; R=Ph, cyclohexyl; M+ =K+ ) give rise to an intense red luminescence.

Luminescent 1D chain of platinum(II) terpyridyl units with p-dithiobenzoquinone organometallic linker: self-aggregation imparted from Pt...Pt/pi-pi interactions.

Unlike p-dithiobenzoquinone (), which is extremely reactive and has never been isolated, the metal-stabilised p-dithiobenzoquinone [Cp*Ir(eta4-C6H4S2)] () was prepared and used as an efficient organometallic linker to construct novel supramolecular assemblies. Treatment of with the electrophilic Pt(II)(terpy) building blocks produced the supramolecular assembly {[Pt(terpy){Cp*Ir-p-(eta4-C6H4S2)}Pt(terpy)][OTf]4}n (), which was fully characterised and its molecular structure was determined by X-ray crystallography. The structure of revealed the presence of pi-pi and Pt[dot dot dot]Pt interactions among individual molecules describing a 1D chain. Complex showed unusual UV/Vis absorption and luminescence behaviour at low temperature, imparted from self-aggregation mediated by pi-pi and Pt...Pt interactions.

Synthesis, characterisation, electrochemistry and luminescence studies of 9-anthrylgold(I) complexes.

Reaction of mono- and dinuclear gold(I) phosphine chloride precursors with an excess of organolithium reagent C14H9Li in dry diethyl ether or THF gave mononuclear [(PPh3)Au(C9H14)] and dinuclear [(P--P)Au2(C14H9)2] (P--P = dppm, dcpm) and [(dcpm)Au2Br(C14H9)], respectively. These complexes were found to be emissive both in the solid state and in fluid solutions.