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1. IR spectroscopic characterization of 3d transition metal carbene cations, FeCH ₂ ⁺ and CoCH ₂ ⁺ : periodic trends and a challenge for DFT approaches

   https://doi.org/10.1039/d4cp00026a  

   Wensink, Frank J; Smink, Corry E; Armentrout, P B; Bakker, Joost M (March 2024, Physical Chemistry Chemical Physics)

   A combination of IR multiple-photon dissociation (IRMPD) action spectroscopy and quantum chemical calculations was employed to investigate the [M,C,2H]⁺(M = Fe and Co) species. 

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2. Ultraviolet Excitation of M-O ₂ (M = Phenalenone, Fluorenone, Pyridine, & Acridine) Complexes Resulting in ¹ O ₂

   https://doi.org/10.1021/acs.jpca.4c00143  

   Parsons, Bradley F.; Hulce, Martin R.; Ackerman, John R.; Reardon, Kylie A.; Pappas, Emerson S.; Kettler, Lauren E. (April 2024, The Journal of Physical Chemistry A)

   In our experiment, a trace amount of an organic molecule (M = 1H-phenalen-1-one, 9-fluorenone, pyridine, or acridine) was seeded into a gas mix consisting of 3% O₂ with a rare gas buffer (He or Ar) and then supersonically expanded. We excited the resulting molecular beam with ultraviolet light at either 355 nm (1H-phenalen-1-one, 9-fluorenone, or acridine) or 266 nm (pyridine) and used resonance enhanced multiphoton ionization (REMPI) spectroscopy to probe for formation of O₂ in the a ¹Δ_g state, ¹O₂. For all systems, the REMPI spectra demonstrates that ultraviolet excitation results in formation of ¹O₂ and the oxygen product is confirmed to be in the ground vibrational state and with an effective rotational temperature below 80 K. We then recorded the velocity map ion image of the ¹O₂ product. From the ion images we determined the center-of-mass translational energy distribution, P(E_T), assuming photodissociation of a bimolecular M-O₂ complex. We also report results from electronic structure calculations that allow for a determination of the M-O₂ ground state binding energy. We use the complex binding energy, the energy to form ¹O₂, and the adiabatic triplet energy for each organic molecule to determine the available energy following photodissociation. For dissociation of a bimolecular complex, this available energy may be partitioned into either center-of-mass recoil or internal degrees of freedom of the organic moiety. We use the available energy to generate a Prior distribution, which predicts statistical energy partitioning during dissociation. For low available energies, less than 0.2 eV, we find the statistical prediction is in reasonable agreement with the experimental observations. However, at higher available energies the experimental distribution is biased to lower center-of-mass kinetic energies compared with the statistical prediction, which suggests the complex undergoes vibrational predissociation. 

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3. Ultracompact 4H-silicon carbide optomechanical resonator with f _m  ·  Q _m exceeding 10 ¹³   Hz

   https://doi.org/10.1364/PRJ.567674  

   Liu, Yuncong; Sun, Wenhan; Abiri, Hamed; Feng, Philip_X-L; Li, Qing (August 2025, Photonics Research)

   Silicon carbide (SiC) has great potential for optomechanical applications due to its outstanding optical and mechanical properties. However, challenges associated with SiC nanofabrication have constrained its adoption in optomechanical devices, as embodied by the considerable optical loss or lack of integrated optical access in existing mechanical resonators. In this work, we overcome such challenges and demonstrate a low-loss, ultracompact optomechanical resonator in an integrated 4H-SiC-on-insulator (4H-SiCOI) photonic platform for the first time, to our knowledge. Based on a suspended 4.3-μm-radius microdisk, the SiC optomechanical resonator features low optical loss (<1  dB/cm), a high mechanical frequencyf_mof 0.95×10⁹  Hz, a mechanical quality factorQ_mof 1.92×10⁴, and a footprint of <1×10⁻⁵  mm². The correspondingf_m·Q_mproduct is estimated to be 1.82×10¹³  Hz, which is among the highest reported values of optomechanical cavities tested in ambient environment at room temperature. In addition, the strong optomechanical coupling in the SiC microdisk enables coherent regenerative optomechanical oscillations at a threshold optical dropped power of 14 μW, which also supports efficient harmonic generation at increased power levels. With such competitive performance, we envision a range of chip-scale optomechanical applications to be enabled by the low-loss 4H-SiCOI platform. 

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4. Organo‐Functionalized Lacunary Double Cubane‐Type Oxometallates: Synthesis, Structure, and Properties of [(M ^II Cl) ₂ (V ^IV O) ₂ {((HOCH ₂ CH ₂ )(H)N(CH ₂ CH ₂ O))(HN(CH ₂ CH ₂ O) ₂ )} ₂ ] (M=Co, Zn)

   https://doi.org/10.1002/chem.202301389  

   Shuaib, Damola T.; Swenson, LaSalle; Kaduk, James A.; Chang, Tieyan; Chen, Yu‐Sheng; McNeely, James; Khan, M. Ishaque (October 2023, Chemistry – A European Journal)

   Abstract Organofunctionalized tetranuclear clusters [(M^IICl)₂(V^IVO)₂{((HOCH₂CH₂)(H)N(CH₂CH₂O))(HN(CH₂CH₂O)₂)}₂] (1, M=Co,2: M=Zn) containing an unprecedented oxometallacyclic {M₂V₂Cl₂N₄O₈} (M=Co, Zn) framework have been prepared by solvothermal reactions. The new oxo‐alkoxide compounds were fully characterized by spectroscopic methods, magnetic susceptibility measurement, DFT and ab initio computational methods, and complete single‐crystal X‐ray diffraction structure analysis. The isostructural clusters are formed of edge‐sharing octahedral {VO₅N} and trigonal bipyramidal {MO₃NCl} units. Diethanolamine ligates the bimetallic lacunary double cubane core of1and2in an unusual two‐mode fashion, unobserved previously. In the crystalline state, the clusters of1and2are joined by hydrogen bonds to form a three‐dimensional network structure. Magnetic susceptibility data indicate weakly antiferromagnetic interactions between the vanadium centers [J_iso(V^IV−V^IV)=−5.4(1); −3.9(2) cm⁻¹], and inequivalent antiferromagnetic interactions between the cobalt and vanadium centers [J_iso(V^IV−Co^II)=−12.6 and −7.5 cm⁻¹] contained in1. 

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5. Spectroscopic and Crystallographic Characterization of the R ₃ N ⁺ −C−H⋅⋅⋅X Interaction

   https://doi.org/10.1002/chem.202103922  

   Capilato, Joseph_N; Harry, Stefan_A; Siegler, Maxime_A; Lectka, Thomas (January 2022, Chemistry – A European Journal)

   Abstract As appreciation for nonclassical hydrogen bonds has progressively increased, so have efforts to characterize these interesting interactions. Whereas several kinds of C−H hydrogen bonds have been well‐studied, much less is known about the R₃N⁺−C−H⋅⋅⋅X variety. Herein, we present crystallographic and spectroscopic evidence for the existence of these interactions, with special relevance to Selectfluor chemistry. Of particular note is the propensity for Lewis bases to engage in nonclassical hydrogen bonding over halogen bonding with the electrophilic F atom of Selectfluor. Further, the first examples of¹H NMR experiments detailing R₃N⁺−C−H⋅⋅⋅X (X=O, N) hydrogen bonds are described. 

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