V-Shaped Tröger Oligothiophenes Boost Triplet Formation by CT Mediation and Symmetry Breaking.

A new family of molecules obtained by coupling Tröger's base unit with dicyanovinylene-terminated oligothiophenes of different lengths has been synthesized and characterized by steady-state stationary and transient time-resolved spectroscopies. Quantum chemical calculations allow us to interpret and recognize the properties of the stationary excited states as well as the time-dependent mechanisms of singlet-to-triplet coupling. The presence of the diazocine unit in Tröger's base derivatives is key to efficiently producing singlet-to-triplet intersystem crossing mediated by the role of the nitrogen atoms and of the almost orthogonal disposition of the two thiophene arms. Spin-orbit coupling-mediated interstate intersystem crossing (ISC) is activated by a symmetry-breaking process in the first singlet excited state with partial charge transfer character. This mechanism is a characteristic of these molecular triads since the independent dicyanovinylene-oligothiophene branches do not display appreciable ISC. These results show how Tröger's base coupling of organic chromophores can be used to improve the ISC efficiency and tune their photophysics.

π-Extended Hexapyrrolylbenzenes: Exploring Charge-Transfer Phenomena in Donor-Acceptor Propellers.

A family of propeller-shaped donor-acceptor hexapyrrolylbenzenes (HPBs) were designed and synthesized by sequential nucleophilic substitution of hexafluorobenzene with π-extended pyrroles. In particular, four hybrids were obtained, containing various combinations of electron-rich and electron-poor acenaphthylene-fused pyrroles. Additionally, to probe the efficiency of ortho transfer interactions, a system was designed containing unique donor and acceptor subunits spatially separated with four unfunctionalized pyrroles. DFT calculations showed propeller-shaped geometries of all HPB molecules and separation of frontier molecular orbitals between donor and acceptor subunits. Steady-state and time-resolved photophysical measurements revealed charge-transfer (CT) character of the emission with strong positive dependence on solvent polarity. The principal CT pathway involves ortho-positioned pairs of donors and acceptors and requires bending of the acceptor in the excited state.

Pyrene-Bridged Expanded Carbaporphyrin Nanobelts.

Two belt-like expanded carbaporphyrins (NB1 and NB2) were prepared via a one-pot procedure that involves a [6 + 3] condensation between a pyrene-bearing tetrapyrrole precursor (2) and pentafluorobenzaldehyde, followed by oxidation. Single crystal X-ray diffraction analyses revealed that NB1 and NB2 both contain six dipyrromethene moieties and three bridging pyrene units. In the structure of NB1, there are two vertically orientated pyrene units and one transverse orientated pyrene unit; however, in NB2 all three pyrene units are vertically orientated. The structural differences between NB1 and NB2 are reflected in their respective physical properties as revealed by proton NMR, UV-vis, and fluorescence spectroscopies. In contrast to all-carbon nanobelts, NB1 and NB2 contain multiple pyrrolic nitrogen donors that could serve as potential metal coordination sites. As a test of this possibility, NB2 was used to prepare an unprecedented Zn complex containing 7 Zn2+ metal centers connected by a network of bridging atoms, as confirmed by a single crystal X-ray diffraction analysis. To the best of our knowledge, this is the first example of a belt-like molecular system that can coordinate multiple metal ions both along the backbone and within its central cavity.

Charge-Delocalized State and Coherent Vibrational Dynamics in Rigid PBI H-Aggregates.

Herein, the ultrafast photoinduced dynamics and vibrational coherences for two perylenebisimide (PBI) H-aggregates showcase the formation of the excimer state and the delocalized radical anion state in the excited state, respectively. Using femtosecond transient absorption (fs-TA) and time-resolved impulsive stimulated Raman scattering (TR-ISRS) measurements, we unveiled excited-state dynamics of PBI H-aggregates in two aspects: (1) the intermolecular interactions between PBI units in H-aggregates induce the formation of new excited states, excimer and delocalized radical anion states, and (2) the intermolecular out-of-plane along the aggregate axis and the PBI core C═C stretch Raman modes can be a crucial indicator to understand the coherent exciton dynamics in H-aggregates. Notably, those excited-state Raman modes showed stationary peak positions during the excited-state dynamics. TR-ISRS analysis provides insights into the excited-state vibrational coherences concerning the formation of the excimer and charge-delocalized state in each aggregate system.

An Electron-Accepting aza-BODIPY-Based Donor-Acceptor-Donor Architecture for Bright NIR Emission.

A bright near-infrared (NIR) fluorescent molecule was developed based on the donor-acceptor-donor (D-A-D) approach using an aza-BODIPY analog called pyrrolopyrrole aza-BODIPY (PPAB) as an electron-accepting chromophore. Directly introducing electron-donating triphenylamine (TPA) to develop a D-A-D structure caused redshifts of absorption and emission of PPAB into the NIR region with an enhanced fluorescence brightness of up to 5.2×104  m-1 cm-1 , whereas inserting a phenylene linker between the TPA donor and the PPAB acceptor induced solvatochromic behavior in emission. Transient absorption spectra and theoretical calculations revealed the presence of a highly emissive hybridized locally excited and charge-transfer state in the former case and the contribution of the dark charge-separated state to the excited state in the latter case. The bright D-A-D PPAB as a novel emitter resulted in a NIR electroluminescence with a high external quantum efficiency of 3.7 % and a low amplified spontaneous emission threshold of ca. 80 µJ cm-2 , indicating the high potential for NIR optoelectronic applications.

A Light-Harvesting/Charge-Separation Model with Energy Gradient Made of Assemblies of meta-Pyridyl Zinc Porphyrins.

Self-assembly of porphyrins is a fascinating topic, not only for mimicking chlorophyll assemblies in photosynthetic organisms, but also for the potential of creating molecular-level devices. Herein, zinc porphyrin derivatives bearing a meta-pyridyl group at the meso position were prepared and their assemblies studied in chloroform. Among the porphyrins studied, one with a carbamoylpyridyl moiety gave a distinct 1 H NMR spectrum in CDCl3 , which allowed the supramolecular structure in solution to be probed in detail. Ring-current-induced chemical-shift changes in the 1 H NMR spectrum, together with vapor-pressure osmometry and diffusion-ordered NMR spectroscopy, among other evidence, suggested that the porphyrin molecules form a trimer with a triangular cone structure. Incorporation of a directly linked porphyrin-ferrocene dyad with the same assembling properties in the assemblies led to a rare example of a light-harvesting/charge-separation system in which an energy gradient is incorporated and reductive quenching occurs.

Dual Emission of a Free-Base 5-Oxaporphyrinium Cation from its cis- and trans-NH Tautomers.

Replacement of the meso methine carbon atoms of porphyrins with heteroatoms is a powerful strategy for tuning their optical and electronic properties. In particular, 5-oxaporphyrin is an attractive target due to its importance as an intermediate in heme catabolism. In this work, we describe the synthesis and properties of a free-base 5-oxaporphyrinium cation, which was prepared by the ring-closure of a bilindione with trifluoromethanesulfonic anhydride. This free-base 5-oxaporphyrinium cation exhibits dual fluorescence originating from its unique NH tautomerism. In contrast to normal porphyrins, the cis form of the 5-oxaporphyrinium cation is more stable than the trans form due to the effective delocalization of its positive charge. We thus demonstrate here that meso-modified heteroporphyrins enable the manipulation of NH tautomerism in porphyrinic macrocycles.

Tetrameric and Hexameric Porphyrin Nanorings: Template Synthesis and Photophysical Properties.

Hexameric and tetrameric porphyrin nanorings, Z6·T6 and Z4·T4, were synthesized in 53% and 14% yields, respectively, by the Sonogashira-type self-oligomerization of porphyrin monomer 1 using hexadentate template T6 and tetrapyridylporphyrin template T4. Template-free nanorings Z6 and Z4 were also prepared. The femtosecond transient absorption measurements revealed fast excitation energy hopping (EEH) along these nanorings with hopping rates of 2-5 ps. Treatment of Z6 with chiral template CT6 gave Z6·CT6 showing circular dichroism (CD) and circularly polarized luminescence (CPL) in the absorption and fluorescence regions of Z6, respectively, which indicates chirality transfer from CT6 to Z6.

Site-Selective N-Methylation of 5,15-Diazaporphyrins: Reactive Cationic Porphyrinoids that Provide Isoporphyrin Analogues.

N-Alkylation significantly changes the electronic and optical properties, as well as the reactivity of nitrogen-containing π-conjugated molecules. In this study, it is found that treating 5,15-diazaporphyrins with methyl triflate selectively affords the corresponding N-methyl-5,15-diazaporphyrinium cations in good yield. N-Methylation substantially alters the electronic properties and reactivity of diazaporphyrins. The electron-accepting properties of the N-methyl-5,15-diazaporphyrinium cations are enhanced due to their lowered LUMO level. Stabilization of the LUMO energy enables regio- and stereoselective Diels-Alder reactions of the cationic diazaporphyrin with cyclopentadiene. N-Methylation also enhances the acidity of the inner NH protons, and thus, allows facile deprotonation to provide nitrogen-substituted isoporphyrin analogues with only one NH group in the central cavity.

Tracking Structural Evolution during Symmetry-Breaking Charge Separation in Quadrupolar Perylene Bisimide with Time-Resolved Impulsive Stimulated Raman Spectroscopy.

Elucidating structural roles in photoinduced charge transfer is indispensable, as nuclear rearrangements are simultaneously usually involved in the dynamics. However, it is hard to evaluate whether the structural changes occur or not by using conventional time-resolved electronic spectroscopy. Here, time-resolved impulsive stimulated Raman spectroscopy is applied to record the evolution of vibrational snapshots during charge-separation dynamics of donor-acceptor-donor-type quadrupolar perylene bisimide in real time. Drastic frequency shifts were observed for several Raman bands with their population kinetics, thus symmetry-breaking charge separation accompanies significant structural changes, as supported by (TD)-DFT calculations. A comparison between time-resolved Raman spectra of the neutral S1 state and the radical anion species shows that the spectral signatures, especially in high-frequency regions, provide important clues to bond length alternation patterns in the PBI core.

Bonding Evaluation Between Nanotube by Anodic Oxidation and Machined Dental Titanium Implant in Beagle Dog.

This study is to evaluate the bonding test between nanotube surface and machined dental titanium implant during the clinical procedure in beagle dog. A total of 24 screw-shaped implants (4 mm in diameter and 8.5 mm in length) were used. The implants were classified into 2 groups (n = 12): machined surface (M group) and nano surface which is nanotube formation on the machined surface (MA group). Anodic oxidation was performed at a 20 V for 10 min with 1 M H3PO4 and 1.5 wt% HF solutions. The implant were installed on beagle dog's humerus. After 4 and 12 weeks later, the beagle dog is sacrificed and the implant were removed with torque force. The removed implant was evaluated by SEM and EDX to observe the implant surface and nanotube's deformation. By investigating removed implant surfaces using SEM and EDX, M group was partially covered with bone, and MA groups were completely covered with bone. Nanotube was not shown any deformity. It indicated that nanotube showed good bonding stability with dental titanium implant.

Successful management of proteinuria and systemic hypertension in a dog with renal cell carcinoma with surgery, telmisartan, and amlodipine.

An 11-year-old neutered male Yorkshire terrier dog was presented with a 3-week history of hematuria and anorexia. A unilateral renal mass was detected and surgically removed. The renal mass was diagnosed on histopathologic examination as a renal carcinoma. Supportive medical therapy was carried out and persistent systemic hypertension was managed using telmisartan.

Gestion réussie de la protéinurie et de l'hypertension systémique chez un chien atteint d'un carcinome rénal à l'aide d'une chirurgie, de telmisartan et d'amlodipine. Un chien Yorkshire terrier mâle stérilisé âgé de 11 ans a été présenté avec une anamnèse de 3 semaines d'hématurie et d'anorexie. Une masse rénale unilatérale a été détectée et excisée par chirurgie. La masse rénale a été diagnostiquée à l'examen histopathologique comme étant un carcinome rénal. Une thérapie médicale de soutien a été réalisée et l'hypertension systémique persistante a été gérée à l'aide de telmisartan.(Traduit par Isabelle Vallières).

Growth-inhibition patterns and transfer-factor profiles in arsenic-stressed rice (Oryza sativa L.).

Arsenic (As) accumulation in rice owing to uptake from the soil is a critical human health issue. Here, we studied the chemical properties of As-treated soils, growth inhibition patterns of As-stressed rice plants, changes in the As content of soil and soil solutions, and the relationship between As accumulation and As transfer factor from the soil to the rice organs. Rice plants were cultivated in a greenhouse under four concentrations of As: 0 (control), 25, 50, and 75 mg kg-1. A significant positive correlation was found between available P2O5 and exchangeable K and between As concentration and available P2O5 or exchangeable K. The As concentration for 50% shoot growth inhibition was 50 mg kg-1. As levels in roots and shoots were positively correlated with the growth stages of rice. The transfer factor (TF)root/soil increased with As concentration at the tillering stage but decreased at the heading stage. TFroot/soil and TFshoot/soil were higher at the heading stage than at the tillering stage. As accumulation in the 25 mg kg-1 treatment was higher during the heading stage, whereas no difference was found at the tillering stage. As accumulation was related to plant biomass and soil As concentration. We found that As accumulation was greater at As concentrations that allowed for plant growth and development. Thus, species-specific threshold concentrations must be determined based on As phytotoxicity for the phytoremediation of As-contaminated soils. Hence, developing practical approaches for managing safe crop production in farmlands with an As contamination of 25 mg kg-1 or less is necessary.

Histological Evaluation of Nano-Micro Titanium Implant Surface Treatment in Beagle Humerus.

The objective of this study was to investigate the effects of nano-micro titanium implant surface using histology in beagle dogs. A total of 48 screw-shaped implants (Megagen, Daegu, Korea) which dimensions were 4 mm in diameter and 8.5 mm in length, were used. The implants were classified into 4 groups (n = 12): machined surface (M group), RBM (Resorbable Blasting Media) surface (R group), nano surface which is nanotube formation on the machined surface (MA group) and nano-micro surface which is nanotube formation on the RBM surface (RA group). Anodic oxidation was performed at a constant voltage of 20 V for 10 min using a DC power supply (Fine Power F-3005; SG EMD, Anyang, Korea). The bone blocks were investigated using histology. There was no inflammation around implants, and new bone formation was shown along with the nano-micro titanium implant surfaces. The amount of bone formation was increased depending on time comparing 4 weeks and 12 weeks. At 12 weeks, lamellar bone was more formed along with the nano-micro titanium implant surfaces than 4 weeks. It indicated that nano-micro surface showed good result in terms of osseointegration.

MicroCT Analysis of Micro-Nano Titanium Implant Surface on the Osseointegration.

This study was to investigate the effects of micro-nano titanium implant surface on the osseointegration. A total of 36 screw-shaped implants were used. The implant surfaces were classified into 3 groups (n = 12): machined surface (M group), nanosurface which is nanotube formation on the machined surface (MA group) and nano-micro surface which is nanotube formation on the RBM surface (RA group). Anodic oxidation was performed at a 20 V for 10 min with 1 M H3PO4 and 1.5 wt% HF solutions. The implants were installed on the humerus on 6 beagles. After 4 and 12 weeks, the morphometric analysis with micro CT (skyscan 1172, SKYSCAN, Antwerpen, Belgium) was done. The data were statistically analyzed with two-way ANOVA. Bone mineral density and bone volume were significantly increased depending on time. RA group showed the highest bone mineral density and bone volume at 4 weeks and 12 weeks significantly. It indicated that nano-micro titanium implant surface showed faster and more mature osseointegration.

Analysis of Removal Torque of Injection Molded Zirconia Implants; An Experimental Study on Beagles.

This study compared the removal torque between injection molded zirconia implants and titanium implants with resorbable blast media (RBM) surfaces in beagle humeri. Fifteen screw-shaped implants were classified into 3 groups; titanium implant with RBM surface (Group RT), injection molded zirconia implant (Group Zr) and injection molded zirconia implant with sand-blasted surface (Group ZrS). Implants were inserted into beagle humeri. After 12 weeks, removal torque values were measured. The Zr group has a slightly higher removal torque value than the RT and ZrS groups but there were no significant differences among groups. Zirconia implants shows a similar removal torque to RBM titanium implants. This in vivo study showed injection molded zirconia implants could be an alternative to RBM titanium implants in terms of removal torque.

Impact of Packing Geometry on Excimer Characteristics and Mobility in Perylene Bisimide Polycrystalline Films.

Efficient exciton transport is essential for high-performance optoelectronics. Considerable efforts have been focused on improving the exciton mobility in organic materials. While it is feasible to improve mobility in organic systems by forming well-ordered stacks, the formation of trap states, particularly the lower-lying states referred to as excimers, remains a significant challenge to enhancing mobility. The mobility of excimer excitons intricately depends on the strength of excitonic coupling in terms of Förster-type diffusive exciton transfer processes. Given that the formation and mobility of excimer excitons are highly sensitive to molecular arrangements (packing geometries), conducting comprehensive investigations into the structure-property relationship in organic systems is crucial. In this study, we prepared three types of polycrystalline films of perylene bisimide (PBI) by varying substituents at the imide and bay positions, which allowed us to tailor the properties of excimer excitons and their mobility based on packing geometries and excitonic coupling strengths. By utilizing femtosecond transient absorption spectroscopy, we observed ultrafast excimer formation in the higher coupling regime, while in the lower coupling regime, the transition from Frenkel to excimer excitons occurs with a time constant of 500 fs. Under high pump-fluence, exciton-exciton annihilation processes occur, indicating the diffusion of excimer excitons. Intriguingly, employing a three-dimensional diffusion model, we derived a diffusion constant that is 3000 times greater in the high coupling regime than in the low coupling regime. To investigate the optoelectronic properties in the form of a bulk system, we fabricated n-type organic field effect transistors and obtained 8000 times higher mobility in the high coupling regime. Furthermore, photocurrent measurements enable us to investigate the charge carrier transport by mobile excimer excitons, suggesting a 230-fold improvement in external quantum efficiency with tightly packing PBI molecules compared to the low coupling regime. These findings not only offer valuable insights into optimizing organic materials for optoelectronic devices but also unveil the intriguing potential of exciton migration within excimers.

Titanium dioxide nanotube modified implants: an animal study on bone formation.

This study examined the bone response to titanium dioxide nanotube modified implants. A total of 24 implants were placed in the femur of 4 beagles. Before placement, screw-shaped implants were classified into 3 groups; machined surface (group M), titanium dioxide nanotube modification of the machined surface (group MN) and titanium dioxide nanotube modification of the RBM surface (group RN). The texture morphology was observed via scanning electron microscopy. Animals were euthanized after 4 and 12 weeks of submerged healing and the histologic and histomorphometric analyses were performed. Groups MN and RN showed a significantly higher percentage of mineralized bone than that in group M (p < 0.05). The results of this in vivo study constitute significant evidence that the presence of the titanium dioxide nanotubes enhance osseointegration of implants.

The effect of rhBMP-2 and PRP delivery by biodegradable ß-tricalcium phosphate scaffolds on new bone formation in a non-through rabbit cranial defect model.

This study evaluated whether the combination of biodegradable ß-tricalcium phosphate (ß-TCP) scaffolds with recombinant human bone morphogenetic protein-2 (rhBMP-2) or platelet-rich plasma (PRP) could accelerate bone formation and increase bone height using a rabbit non-through cranial bone defect model. Four non-through cylindrical bone defects with a diameter of 8-mm were surgically created on the cranium of rabbits. ß-TCP scaffolds in the presence and absence of impregnated rhBMP-2 or PRP were placed into the defects. At 8 and 16 weeks after implantation, samples were dissected and fixed for analysis by microcomputed tomography and histology. Only defects with rhBMP-2 impregnated ß-TCP scaffolds showed significantly enhanced bone formation compared to non-impregnated ß-TCP scaffolds (P < 0.05). Although new bone was higher than adjacent bone at 8 weeks after implantation, vertical bone augmentation was not observed at 16 weeks after implantation, probably due to scaffold resorption occurring concurrently with new bone formation.

Aromatic-bridged and meso-meso-linked BF2-smaragdyrin dimers exhibit fast decays in polar solvents by symmetry-breaking charge transfer.

Symmetry-breaking charge transfer is one of the key process in photosynthetic reaction centers and specific artificial optoelectronic devices such as dye-sensitized solar cells. Here we report the synthesis of aromatic-bridged BF2-smaragdyrin dimers, meso-free BF2-smaragdyrin, and its meso-meso-linked BF2-smaragdyrin dimer. The decays of S1-states of these dimers are accelerated with an increase in solvent polarity and a decrease in the distance between the two BF2-smaragdyrin units, suggesting symmetry-breaking charge transfer. The fluorescence lifetimes of the dimers become shortened in polar solvents. However, ultrafast transient absorption spectroscopy do not detect charge-separated ion pairs. On the basis of these results, we conclude that the decays of the excited states of the BF2-smaragdyrin dimers are accelerated by solvation-induced symmetry-breaking charge transfer, depending on the degree of the electronic interaction between the smaragdryin units as a rare case for porphyrinoids. The degree of charge transfer is larger for dimers with larger electronic interactions.