A novel metal-free amorphous room-temperature phosphorescent polymer without conjugation

Hydrogen-bond organized 2D metal-organic microsheets: direct ultralong phosphorescence and color-tunable optical waveguides

Ultralong phosphorescent materials have numerous applications across biological imaging, light-emitting devices, X-ray detection and anti-counterfeiting. Triplet-state molecular phosphorescence typically accompanies the singlet-state fluorescence during photoluminescence, and it is still difficult to achieve direct triplet photoemission as ultralong room temperature phosphorescence (RTP). Here, we have designed Zn-IMDC (IMDC, 4,5-imidazoledicarboxylic acid) and Cd-IMDC, two-dimensional (2D) hydrogen-bond organized metal-organic crystalline microsheets that exhibit rarely direct ultralong RTP upon UV excitation, benefiting from the appropriate heavy-atom effect and multiple triplet energy levels. The excitation-dependent and thermally stimulated ultralong phosphorescence endow the metal-organic systems great opportunities for information safety application and temperature-gated afterglow emission. The well-defined 2D microsheets present color-tunable and anisotropic optical waveguides under different excitation and temperature conditions, providing an effective way to obtain intelligent RTP-based photonic systems at the micro- and nano-scales.

Cucurbit[10]uril-Based Orthogonal Supramolecular Polymers with Host-Guest and Coordination Interactions and Its Applications in Anion Classification

A novel orthogonal supramolecular polymer (Q[10]-TPDPB-Lu³⁺) in a host-guest ratio of 2:1 was successfully constructed utilizing the specificity and excellent cavity matching of Q[10] with the tripyridine derivatives (TPDPB). Significantly, non-covalent interactions between Q[10]'s hydrophobic cavities and Lu³⁺ were used to induce charge transfer of TPDPB to TPDPB and TPDPB to Lu³⁺, resulting in the construction of structurally interesting orthogonal assemblies with excellent fluorescence properties. Finally, the Q[10]-TPDPB-Lu³⁺ assemblies were shown to have good recognition and classification of strong and weak acid anions as well as iodide anions, and the classification was accompanied by a clear fluorescence emission change allowing visual observation.

Triplet exciton dynamics of pure organics with halogen substitution boosted two photon absorption and room temperature phosphorescence: A theoretical perspective

Organic room temperature phosphorescence (RTP) molecules have shown promising applications in organic light emitting diodes and vivo imaging. Thus, triplet exciton dynamics in solid phase should be revealed and the molecule should possess large two photon absorption (TPA) cross sections under near-infrared excitation. The effects of halogen substitution and intermolecular interaction on RTP and TPA properties are studied at molecular level for a series of derivatives. Surrounding environment in solid phase is considered by combined quantum mechanics and molecular mechanics method. Intermolecular interactions are evaluated by the independent gradient model and calculated through the molecular force field energy decomposition method. Minimum energy crossing point, Huang-Rhys factor and reorganization energy are discussed, triplet exciton dynamics are investigated by thermal vibration correlation function method. Results indicate that the largest TPA cross sections are found for molecule in water. The halogen substitution can enlarge the proportion of (π, π*) and facilitate the intersystem crossing process. Restricted intramolecular rotation motions of dihedral angle in low frequency regions are found for Br-Np-Cz-BF₂ in solid phase. While enhanced vibrations of bond length and bond angle in high frequency regions are detected for I-Np-Cz-BF₂. Effects of halogen substitution and intermolecular interaction on triplet exciton dynamics are highlighted.

Room Temperature Phosphorescence Emission From Multi-States

Organic room temperature phosphorescence (RTP) materials have received considerable attention due to their fascinating photophysical properties. During the past decade, various organic luminogens exhibiting RTP emission in solid states were reported. However, the phosphorescence emission of organic compounds can hardly be observed in their solutions at room temperature. Herein, we reported two fluorene derivatives that can emit RTP in degassed organic solvents, polymer doped film, and crystalline states. Furthermore, those RTP luminogens emitted different colors with different phosphorescence lifetimes in multi-states. These results indicated that the phosphorescence performance can be adjusted flexibly in different condensed states. To our knowledge, this is the first example possessing diverse organic RTP at multi-states, including solution state.

Modulating the optical properties and functions of organic molecules through polymerization

Organic functional materials with advanced optical properties have attracted much attention due to their broad applications, such as in light-emitting diodes, solar cells, anti-counterfeiting, photocatalysis, and even disease diagnosis and treatment. Recent research has revealed that many optical properties of organic molecules can be improved through simple polymerization. In this review, we discuss the phenomenon, mechanism, and impact of polymerization on the properties of materials, including the polymerization-induced spectral shift, polymerization-enhanced photosensitization, polymerization-enhanced two-photon absorption, polymerization-enhanced photocatalytic efficiency, polymerization-induced room temperature phosphorescence, polymerization-induced thermally activated delayed fluorescence, and polymerization-induced emission using specific examples with different applications. The new opportunities arising from polymerization in designing high performance optical materials are summarized in the future perspective.

Highly Efficient Heavy Atom Free Room Temperature Phosphorescence by Host-Guest Doping

Recently, there has been remarkable progress of the host-guest doped pure organic room-temperature phosphorescence (RTP) materials. However, it remains a great challenge to develop highly efficient host-guest doping systems. In this study, we have successfully developed a heavy atom free pure organic molecular doped system (benzophenone-thianthrene, respectively) with efficient RTP through a simple host-guest doping strategy. Furthermore, by optimizing the doping ratios, the host-guest material with a molar ratio of 100:1 presented an efficient RTP emission with 46% quantum efficiency and a long lifetime of up to 9.17 ms under ambient conditions. This work will provide an effective way to design new organic doping systems with RTP.

Investigating phosphorescence capability of halogen-substituted metal-free organic molecules: A theoretical study

The radiative and non-radiative decay processes of five compounds are investigated through a comprehensive computational approach, for the aim of investigating the effect of different halogen substituents to the phosphorescent emission. Their optimal configurations at the ground (S₀) and lowest triplet excited (T₁) states are obtained and the calculated phosphorescent emission spectra are comparable with the experimental values. For 1,4-di(9H-carbazol-9-yl)benzene (PDCz), the electronic transition is between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), while for the four halides, the electronic transitions are attributed to several molecular orbitals. According to calculations, 9,9'-(2,5-diiodo-1,4-phenylene)bis(9H-carbazole) (PDICz) possesses the largest radiative decay rate constant (k_r) and non-radiative decay rate constant (k_nr), which can be attributed to the strong spin-orbital coupling from the heavy iodine atom. However, the phosphorescent quantum efficiency (Φ) of PDICz is lower than that of 9,9'-(2,5-dibromo-1,4-phenylene)bis(9H-carbazole) (PDBCz), implying that a comprehensive consideration is necessary. Furthermore, by analyzing the vibrational mode, we have confirmed that the reorganization energies are also influenced by the different halogen atoms. While the dominated factor that determines the k_r and k_nr comes from the spin-orbital coupling. We expect that our research findings will be beneficial to the newly designed organic phosphorescent materials in the future.

Elucidation of distinct fluorescence and room-temperature phosphorescence of organic polymorphs from benzophenone–borate derivatives

The RTP property of polymorphisms present the different emission derive from the same molecule embed in different intermolecular packings.