Variation of CH stretch frequencies with CH4 orientation in the CH4 − F− complex: multiple resonances as vibrational conical intersections

In the \chem{CH_4 - F^-} complex, an adiabatic separation of the CH stretch frequencies from the \chem{CH_4} orientational coordinates allows the calculation of the four adiabatic CH stretch surfaces. These ab initio calculations reveal (i) a large variation of CH stretch frequencies (\textgreater 100 \wn) in the orientational space and (ii) the existence of four symmetrically equivalent sets of vibrational conical intersections (CIs). Two sets of symmetry-allowed CIs are identified in addition to the symmetry-required CIs at the front- and back-side C$_{3v}$ geometries. These results have implications for the evolution of excited CH vibrations in methane during its approach to a potentially reactive surface

VIBRATIONAL JAHN-TELLER EFFECT IN NON-DEGENERATE ELECTRONIC STATES

The Jahn-Teller theorem footnote{H.~A.~ Jahn, and E.~Teller, textit{Proc.~R.~Soc.~Lond.~A.} underline{textbf{161}},~220, (1937).} states that �All non-linear nuclear configurations are therefore unstable for an orbitally degenerate electronic state.� In 1982, Kellman footnote{M.~E.~ Kellman, textit{Chem.~Phys.~Lett.} underline{textbf{87}},~171, (1982).} realized that the Jahn-Teller theorem also applies to nonlinear molecular species in non-degenerate electronic states when there are high-frequency vibrations that are degenerate at a symmetrical reference geometry. When those high frequencies can be considered as adiabatic functions of degenerate low-frequency coordinates, there is a spontaneous Jahn-Teller distortion that lifts the degeneracy of the high-frequency vibrations. Kellman applied the vibrational Jahn-Teller (vJT) concept to the Van der Waals dimer (SF$_{6}$)$_{2}$. In this talk, the vJT concept is applied to E $otimes$ e systems that are small bound molecules in non-degenerate electronic states. The first case considered in systems for which the global minimum of the electronic potential has C$_{3v}$ symmetry.For such systems, including (C$_{6}$H$_{6}$)Cr(CO)$_{3}$ and CH$_{3}$CN, the vJT effect leads to a significant splitting of the degenerate high-frequency vibrations (CH or CO stretches), but the spontaneous vJT distortion is exceptionally small. The second case in systems for which the global minimum of the electronic potential is substantially distorted from the C$_{3v}$ reference geometry. For the second case systems, including CH$_{3}$OH and CH$_{3}$SH, the vJT splitting of the degenerate CH stretches is much larger, on the order of several 10ﾀﾙs of cm$^{-1}$). For both cases, there is the symmetry-required vibrational conical intersection at the C$_{3v}$ reference geometry. For the second case systems, there are additional symmetry-allowed vibrational conical intersections far from the C$_{3v}$ geometry but energetically accessible to the molecule at thermal energies. For both cases, the vibrationally adiabatic surfaces, including the multiple conical intersections, are well described by modest extensions to a high-order Hamiltonian that was developed for the electronic Jahn-Teller problem.footnote{A.~ Viel, and W.~Eisfeld, textit{J.~Chem.~Phys.} underline{textbf{120}},~4603, (2004).

An Extended Jahn-Teller Hamiltonian for Large-Amplitude Motion: Application To Vibrational Conical Intersections in CH3SH and CH3OH

An extended Jahn-Teller Hamiltonian is presented for the case where the (slow) nuclear motion extends far from the symmetry point and may be described approximately as motion on a sphere. Rather than the traditional power series expansion in the displacement from the C3v symmetry point, an expansion in the spherical harmonics is employed. Application is made to the vibrational Jahn-Teller effect in CH3XH, with X = S, O, where the equilibrium CXH angles are 83° and 72°, respectively. In addition to the symmetry-required conical intersection (CI) at the C3v symmetry point, ab initio calculations reveal sets of six symmetry-allowed vibrational CIs in each molecule. The CIs for each molecule are arranged differently in the large-amplitude space, and that difference is reflected in the infrared spectra. The CIs in CH3SH are found in both eclipsed and staggered geometries, whereas those for CH3OH are found only in the eclipsed geometry near the torsional saddle point. This difference between the two molecules is reflected in the respective high-resolution spectra in the CH stretch fundamental region

Mechanochemistry-Driven Construction of Aza-fused π-Conjugated Networks Toward Enhanced Energy Storage

The current approaches toward synthesis of conjugated microporous polymers (CMPs) functionalized by aza-fused functionalities are still limited to solution-based procedures or ionothermal polymerizations, which requires monomers with rigid/high steric hindrance structures and multiple reactive sites and extra arene-based cross-linkers, and generated CMPs with low content of aza-fused functionalities. Herein, a facile mechanochemistry-driven procedure is developed capable of affording a series of CMPs composed of abundant aza-fused functionalities via a homocoupling process. Simple and linear aromatic bromide monomers with phenanthroline or bipyridine cores are deployed as the starting materials, which can coordinate on the metal surface to form 3D assembly and be polymerized in the presence of catalytic amount of magnesium powder driven by mechanochemical treatment under solvent- and additive-free conditions. CMPs composed of solely phenanthroline or bipyridine moieties being connected by C–C bonds are afforded with high surface areas (up to 789 m2 g-1), permanent and hierarchical porous architectures (micro- and mesopores), abundant aza-fused moieties, and π-conjugated networks. All these unique features made them promising candidates as supercapacitors, which exhibit outstanding electrocapacitive performance with a capacitance of 296 F g-1 at 0.3 A g-1 and capacitance retention of 103% for 5000 cycles at 5 A g-1.This is a manuscript of an article published as Fan, Juntian, Tao Wang, Hao Chen, Zongyu Wang, Bishnu P. Thapaliya, Takeshi Kobayashi, Yating Yuan, Ilja Popovs, Zhenzhen Yang, and Sheng Dai. "Mechanochemistry‐Driven Construction of Aza‐fused π‐Conjugated Networks Toward Enhanced Energy Storage." Advanced Functional Materials 32, no. 32 (2022): 2202669. DOI: 10.1002/adfm.202202669. Copyright 2022 Wiley-VCH GmbH. Posted with permission. DOE Contract Number(s): AC05-00OR22725; AC02-07CH11358

Fully Conjugated Poly(phthalocyanine) Scaffolds Derived from a Mechanochemical Approach Towards Enhanced Energy Storage

Phthalocyanines (Pc)-derived materials represent an attractive category of porous organic scaffolds featured by extensive π-conjugated networks, but their construction is still limited to the solution-based pathways, producing materials with inferior conductivity and porosity. Herein, a mechanochemistry-driven approach was developed leveraging the on-surface polymerization of aromatic nitrile monomers with ortho-positioned dicyano groups in the presence of metal catalysts (magnesium, zinc, or aluminum) under neat and ambient conditions. Diverse Pc-functionalized conjugated porous networks (Pc-CPNs) were obtained featured by extensively and fully π-conjugated skeletons, high surface areas, and hierarchical porosities. The monomers in this mechanochemical approach could be extended to those difficult to be handled in solution-based procedures. The Pc-CPNs displayed attractive electrochemical performance as supercapacitor and anodes in batteries, together with superb long-term stability.This is a manuscript of an article published as Fan, Juntian, Tao Wang, Bishnu P. Thapaliya, Liqi Qiu, Meijia Li, Zongyu Wang, Takeshi Kobayashi, Ilja Popovs, Zhenzhen Yang, and Sheng Dai. "Fully Conjugated Poly (phthalocyanine) Scaffolds Derived from a Mechanochemical Approach Towards Enhanced Energy Storage." Angewandte Chemie International Edition 61, no. 38 (2022): e202207607. DOI: 10.1002/anie.202207607. Copyright 2022 Wiley-VCH GmbH. Posted with permission. DOE Contract Number(s): AC02-07CH11358; AC05-00OR22725

Construction of Nitrogen-abundant Graphyne Scaffolds via Mechanochemistry-Promoted Cross-Linking of Aromatic Nitriles with Carbide Toward Enhanced Energy Storage

The 2D graphyne-related scaffolds linked by carbon–carbon triple bonds have demonstrated promising applications in the field of catalysis and energy storage due to their unique features including high conductivity, permanent porosity, and electron-rich properties. However, the construction of related scaffolds is still mainly limited to the cross-linking of CaC2 with multiple substituted aromatic halogens and there is still a lack of efficient methodology capable of introducing high-concentration heteroatoms within the architectures. The development of alternative and facile synthesis procedures to afford nitrogen-abundant graphyne materials is highly desirable yet challenging in the field of energy storage, particularly via the facile mechanochemical procedure under neat and ambient conditions. Herein, graphyne materials with abundant nitrogen-containing species (nitrogen content of 6.9–29.3 wt.%), tunable surface areas (43–865 m2 g−1), and hierarchical porosity are produced via the mechanochemistry-driven pathway by deploying highly electron-deficient multiple substituted aromatic nitriles as the precursors, which can undergo cross-linking reaction with CaC2 to afford the desired nitrogen-doped graphyne scaffolds efficiently. Unique structural features of the as-synthesized materials contributed to promising performance in supercapacitor-related applications, delivering high capacitance of 254.5 F g−1 at 5 mV s−1, attractive rate performance, and good long-term stability.This is a manuscript of an article published as Fan, Juntian, Tao Wang, Bishnu P. Thapaliya, Meijia Li, Chi‐Linh Do‐Thanh, Takeshi Kobayashi, Ilja Popovs, Zhenzhen Yang, and Sheng Dai. "Construction of Nitrogen‐abundant Graphyne Scaffolds via Mechanochemistry‐Promoted Cross‐Linking of Aromatic Nitriles with Carbide Toward Enhanced Energy Storage." Small 19, no. 11 (2023): 2205533. DOI: 10.1002/smll.202205533. Copyright 2022 Wiley-VCH GmbH. Posted with permission. DOE Contract Number(s): AC02-07CH1135

Exploring Lead Zirconate Titanate, the Potential Advancement as an Anode for Li-Ion Batteries

Graphite, widely adopted as an anode for lithium-ion batteries (LIBs), faces challenges such as an unsustainable supply chain and sluggish rate capabilities. This emphasizes the urgent need to explore alternative anode materials for LIBs, aiming to resolve these challenges and drive the advancement of more efficient and sustainable battery technologies. The present research investigates the potential of lead zirconate titanate (PZT: PbZr0.53Ti0.47O3) as an anode material for LIBs. Bulk PZT materials were synthesized by using a solid-state reaction, and the electrochemical performance as an anode was examined. A high initial discharge capacity of approximately 686 mAh/g was attained, maintaining a stable capacity of around 161 mAh/g after 200 cycles with diffusion-controlled intercalation as the primary charge storage mechanism in a PZT anode. These findings suggest that PZT exhibits a promising electrochemical performance, positioning it as a potential alternative anode material for LIBs