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In this study, low-temperature EPR spectroscopy and quantum-chemical techniques were employed to investigate multispin systems─1,5-diphenyl-3-(3-nitrenophenyl)-6-oxoverdazyl and 1,5-diphenyl-3-(4-nitrenophenyl)-6-oxoverdazyl─that contain a nitrene center at either a - or -position, respectively. Ground states and magnetic zero-field splitting (ZFS) parameters of these multispin systems were determined by experimental and computational methods. The results indicated that the high-spin quartet state is a ground state, and the quartet-doublet energy gap is close to 10 kcal/mol for the -position of the nitrene group, with ZFS parameters = 0.292 cm and / = 0.002 cm. In contrast, for the -position, the low-spin doublet state is favored with an energy gap of 1 kcal/mol. The observed difference in the ground states could be qualitatively explained by an analysis of the spin density distribution and by delocalization of the unpaired π-electron of the nitrene center. Overall, this study provides valuable insights into the electronic structures and magnetic parameters of such multispin systems.
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http://dx.doi.org/10.1021/acs.jpca.4c06823 | DOI Listing |
J Chem Theory Comput
September 2025
Institute of Physical Chemistry, University of Freiburg, Albertstraß e 21, 79104 Freiburg, Germany.
The accurate computation of high-spin/low-spin gaps remains a challenging task in computational chemistry, with significant implications for both theoretical studies and experimental applications. In this work, we present an exchange-dedicated perturbation theory (EDPT2) that allows an efficient calculation of exchange couplings in magnetic systems. Our approach builds on a previously developed second-order perturbative scheme based on de Loth's formalism but refines the treatment of singlet wave functions by explicitly incorporating ionic determinants in the zeroth-order description.
View Article and Find Full Text PDFJ Chem Phys
August 2025
School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China.
The construction of spin eigenfunctions for multi-spin systems can become highly nontrivial as the system size increases. Recently, a modular tensor diagram approach was proposed to hierarchically decompose the state space in terms of tensorial modules based on spin pairs, resulting in an effectively organized state space and efficiently constructed symmetry-adapted basis states. Here, it is generalized to treat fermion systems with odd numbers of spins.
View Article and Find Full Text PDFAnal Chim Acta
October 2025
Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, Xiamen, 361005, China.
Background: High-resolution one-dimensional (1D) nuclear magnetic resonance (NMR) spectroscopy plays a critical role in enabling the detail analysis of complex samples, precise determination of molecular structures, and investigation of molecular interactions. However, challenges arise when two spins exhibit very similar chemical shifts, potentially interfering with signal separation. Identifying low-concentration components in complex mixtures with overlapping spectral features becomes even more difficult.
View Article and Find Full Text PDFPhys Rev Lett
June 2025
Institute of Physics, Chinese Academy of Sciences, Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China.
Non-Gaussian fluctuations are one of the essential properties of quantum systems. However, the direct detection of non-Gaussian fluctuations has not yet been achieved in experiments since the specific order of correlation has to be isolated from the complex dynamics of the whole system. In this Letter, we measure the second- and fourth-order correlations of ^{13}C nuclear spins around a nitrogen vacancy center in diamond, using the recently developed quantum nonlinear spectroscopy.
View Article and Find Full Text PDFChem Sci
August 2025
Institute of Macromolecular and Organic Chemistry, Ulm University Albert-Einstein-Allee 11 89081 Ulm Germany
We present a new class of luminescent diradicals based on tris(trichlorophenyl)methyl (TTM) cores symmetrically bridged by indolocarbazole donors. These diradicals exhibit pure diradical character and unprecedented photoluminescence quantum yields of up to 18%, addressing key challenges in the development of stable, emissive organic diradicals. Light emitting diradicals represent a formidable challenge for synthetic chemists; for applications as molecular color centers in quantum sensing and as emitters in optoelectronics.
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