Mechanofluorochromic behaviors and latent fingerprint detection of triphenylamine-based compounds with mono-/bis-BF2 fluorophores.

To better understand the relationship between molecular structure of the mono-/bis-BF2-core compounds and mechanofluoroboron behaviors, two pyridine-based difluoroboron compounds with triphenylamine group (TPA-ts-BF2 and TPA-ts-2BF2) were designed and successfully synthesized, which TPA-ts-BF2 including a BF2 fluorophore and TPA-ts-2BF2 containing the bisBF2 fluorophores. Based on the photophysical properties measurements results, it was found that TPA-ts-2BF2 had more excellent intramolecular charge transfer characteristics than that of TPA-ts-BF2, and exhibited significant aggregation-induced emission activity, however, TPA-ts-BF2 displayed typical aggregation-caused quenching phenomenon. Meanwhile, the emission spectrum of the solid powders of TPA-ts-2BF2 was red-shifted 52 nm after grinding, that of TPA-ts-BF2 was red-shifted 46 nm, which was resulted from crystalline state switching to amorphous state. According to the theoretical calculations, we conjectured that TPA-ts-BF2 with uncoordinated amide linkage moiety had a tendency to forming a more twisted conformance and higher molecular polarity, which made that mechanofluorochromic behavior was worse than that of TPA-ts-2BF2. Additionally, TPA-ts-2BF2 was applied to latent fingerprint detection due to its prime aggregation-induced emission property.

Regulating the Flexibility to Assemble Porous Single-Atom Fe-Coordinated Metallopolymers for Efficient Heterogeneous Catalytic Oxidations.

Metallopolymers as organic-inorganic hybrid materials formulated by metal embedding organic polymers show great potential for novel heterogeneous catalysis, in terms of the facile structural design and tunability. Herein, the disadvantage of nonporous stacking of one-dimensional (1D) structures has been suppressed by chain modulation of the 1D metallopolymers, allowing for the convenient construction of porous assemblies with single-atom dispersion and accessible active sites. By postmodification, the Fe/CM-1 catalyst readily synthesized by coordinating the Fe(II) to the twisted chain of 1D Schiff-base polymer possesses expedient flexibility, showing the highest porosity, remarkable heterogeneous recyclability, and thus prominent catalytic activity for the selective oxidation of benzylamine and alcohols. Moreover, control experiments supported by computational studies demonstrated that the unique pincer structure of Fe/CM-1 effectively maintains the valence state of the anchored single-atom iron, facilitating single-electron transfer and promoting efficient iron redox cycling during the catalytic process. Notably, these 1D metallopolymers have the advantage of cost-effectiveness, easy preparation in gram-scale, and utilization in continuous reaction, providing inspirations for facile synthesis of efficient heterogeneous catalysts from the well-developed 1D metallopolymers.

Mechanofluorochromic behaviours of functionalized carbazole-based difluoroboron compounds with different aryl substituents moieties.

To better understand the relationship between molecular structure and mechanofluorochromic characteristics, three carbazole-based N^O-chelated difluoroboron compounds (Cz-S-BF2 , Cz-PhNp-S-BF2 , and Cz-BNp-S-BF2 ) with different aryl substituents moieties were designed and synthesized. The mechanofluorochromic behaviours of Cz-S-BF2 (luminescence from bluish-green to yellowish-green, emission from 504 to 535 nm) without aryl substitution and Cz-PhNp-S-BF2 (luminescence from green and yellow, emission from 521 to 557 nm) with a phenyl-naphthalene group underwent reversible conversion using the grinding-fuming process. For Cz-BNp-S-BF2 this was not apparent due to the well coplanarity of the binaphthalene moiety. Mechanofluorochromic properties were demonstrated through XRD patterns measurement. We envisage that this study will provide a practicable reference to acquire organic molecules with mechanofluorochromic characteristics.

Building N-hydroxyphthalimide organocatalytic sites into a covalent organic framework for metal-free and selective oxidation of silanes.

A novel crystalline covalent organic framework COF-NHPI was built by a bottom-up strategy to guarantee highly ordered embedment of the N-hydroxyphthalimide (NHPI) units as nitroxyl radical organocatalytic sites. The COF-NHPI was demonstrated to be a metal-free, highly selective and heterogeneous catalyst for the efficient oxidation of various silanes to the corresponding silanols. Mechanistic studies revealed that the critical phthalimido N-oxyl radical was generated in situ to govern the catalysis.

Regulating the spin state of single-atom doped covalent triazine frameworks for efficient nitrogen fixation.

Covalent triazine frameworks (CTFs), served as a versatile platform, can form expedient metal-N single-atom coordination sites as promising catalytic centers. To seek out excellent candidate catalysts of M/CTFs (M = Transition metal) for nitrogen reduction reaction (NRR), a "five-step" strategy involving spin states has been established for hierarchical high-throughput screening and reveals strong coordination ability of the CTFs, outstanding conductivity of the M/CTFs, effective adsorption and activation of N2* attributed to the electron transfer and orbital hybridization between the M/CTFs and N2*. Among the potential candidates, the Cr/CTF is screened out to be an excellent one for nitrogen fixation, which can not only inhibit hydrogen evolution reaction (HER) greatly but also has good thermodynamic stability (Eb =  -4.40 eV), narrow band gap (Eg = 0.03 eV), moderate adsorption energy (Ea =  -0.84 eV), large activation energy (ΔGN2* = -0.71 eV) and a theoretical Faradaic efficiency of 100%. The spin state has been confirmed to be an important descriptor of catalytic activity and the two-state reactivity (TSR) is validated to exist in the NRR. Reaction mechanism with different spin states of Cr/CTF has been demonstrated to give a great impact on the nitrogen fixation, providing solid theoretical support for the design of more efficient NRR catalysts.

Delicate and Fast Photochemical Surface Modification of 2D Photoresponsive Organosilicon Metal-Organic Frameworks.

Photoresponsive arylsilanes have been fascinating molecules for decades because of their unique photophysical characteristics and surface chemistry. Here we report the synthesis and fabrication of a crystalline two-dimensional trisilyl metal-organic framework (TSiMOF) orderly installed with the classical photoresponsive hexamethyltrisilane groups on the surface. Irradiated by UV light under air in minutes the fluorescence of the TSiMOF is turned on simultaneously with an intriguing surface transformation from superhydrophobic to hydrophilic. Thus, multifarious luminescent and hydrophilic patterns including logos, characters and Quick Response codes, etc. with good resolution are readily generated on the facilely fabricated TSiMOF film. The mechanism of this transformation is revealed by control experiments that the superficial trimethylsilyl groups suffering photochemical oxidation have been converted to hydroxyl groups.

Synthesis, Structure, and Significant Energy Gap Modulation of Symmetrical Silafluorene-Cored Tetracyanobutadiene and Tetracyanoquinodimethane Derivatives.

A series of symmetrical tetracyanobutadiene and tetracyanoquinodimethane derivatives with a D-A-D'-A-D structural configuration and silafluorene core (D') were designed and readily synthesized via a [2+2] cycloaddition-retroelectrocyclization (CA-RE) reaction. We found that the photophysical properties and HOMO and LUMO energy levels and gaps of the silafluorene derivatives could be profoundly remolded through CA-RE reactions and modulated by varying the peripheral donor units from phenyl, m-dimethoxyphenyl, and N,N-dimethylaniline to triphenylamine groups. After CA-RE reactions, the HOMO-LUMO gaps of 1a-1j are in the range of 1.75-2.78 eV, with significant decreases of 0.52-1.46 eV compared to those of the parent silafluorene compounds 2a-2j. The intriguing crystal structures of 1f and 1j were analyzed and elucidated to show their unique potential porosity. The stability, electrochemical, and computational studies were systematically performed to unveil the reshaped electron-donating and -withdrawing nature in one molecular system. 1h-1j with peripherally strong amino donors exhibit an intense and broad intramolecular charge transfer absorption band in the near-infrared region from 550 to 900 nm. The molecular design and synthesis reported here broaden the types and fields of D-A molecular systems for potential applications in organic optoelectronic devices.

Simultaneous Enantioselective Determination of the Chiral Fungicide Prothioconazole and Its Major Chiral Metabolite Prothioconazole-Desthio in Food and Environmental Samples by Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry.

An efficient and sensitive chiral analytical method was established for the determination of the chiral fungicide prothioconazole and its major chiral metabolite prothioconazole-desthio in agricultural and environmental samples using ultraperformance liquid chromatography-tandem mass spectrometry. The optical rotation and absolute configuration of enantiomers were identified by optical rotation detector and electronic circular dichroism spectra. The elution order of prothioconazole and its chiral metabolite enantiomers was R-(+)-prothioconazole-desthio, S-(-)-prothioconazole-desthio, R-(-)-prothioconazole, and S-(+)-prothioconazole. The mean recoveries from the samples was 71.8-102.0% with intraday relative standard deviations (RSDs) of 0.3-11.9% and interday RSDs of 0.9-10.6%. The formation of prothioconazole-desthio was studied in soil under field conditions and enantioselective degradation was observed for chiral prothioconazole. Remarkable enantioselective degradation was observed: R-prothioconazole degraded preferentially with EF values from 0.48 to 0.37. Although prothioconazole-desthio is the most remarkably bioactive metabolite, no obvious enantioselective behavior was observed in soil. These results may help to systematically evaluate prothioconazole and its metabolites in food and environmental safety.

N-(7-Methyl-1,8-naphthyridin-2-yl)acetamide-acetic acid (1/1).

In the title adduct, C11H11N3O·C2H4O2, all non-H atoms of the acetamide mol-ecule are roughly coplanar, with an r.m.s. deviation of 0.0720 Å. The dihedral angle between the ring plane and the acetamide group is 8.5 (2)°. In the crystal, O-H⋯N and N-H⋯O hydrogen bonds link the acetamide and acetic acid mol-ecules.

N-(7-Dibromo-methyl-5-methyl-1,8-naphthyridin-2-yl)acetamide-pyrrolidine-2,5-dione (1/1).

In the title co-crystal, C(12)H(11)Br(2)N(3)O·C(4)H(5)NO(2), the naphthyridine derivative and the pyrrolidine-2,5-dione mol-ecules have crystallographic mirror-plane symmetry with all non-H atoms, except the Br atom, located on the mirror plane. In the crystal, N-H⋯N, N-H⋯O and C-H⋯O hydrogen bonds link the mol-ecules into heterodimers. These dimers are further linked into a one-dimensional structure along [010] by weak C-Br⋯O inter-actions [Br⋯O = 3.028 (5) Šand C-Br⋯O = 158.52 (4)°].

Large Stokes shift induced by intramolcular charge transfer in N,O-chelated naphthyridine-BF2 complexes.

Novel N,O-chelated naphthyridine-BF(2) complexes with push-pull structures have been synthesized and characterized. Spectral investigations on these complexes reveal that photoinduced intramolecular charge transfer occurs and results in a large Stokes shift, which is further supported by density functional theory based theoretical calculations.