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Co(acac)2(H2O)2 (1, acac = acetylacetonate), a transition metal complex (S = 3/2), displays field‐induced slow magnetic relaxation as a single‐molecule magnet. For 1 and its isotopologues Co(acac)2(D2O)2 (1‐d4) and Co(acac‐d7)2(D2O)2 (1‐d18) in approximately D4h symmetry, zero‐field splitting of the ground electronic state leads to two Kramers doublets (KDs): lower energy MS = ±1/2 (ϕ1,2) and higher energy MS = ±3/2 (ϕ3,4) states. This work employs inelastic neutron scattering (INS), a unique method to probe magnetic transitions, to probe different magnetic excitations in 1‐d4 and 1‐d18. Direct‐geometry, time‐of‐flight Disk‐Chopper Spectrometer (DCS), with applied magnetic fields up to 10 T, has been used to study the intra‐KD transition as a result of Zeeman splitting, MS = –1/2 (ϕ1) → MS = +1/2 (ϕ2), in 1‐d18. This is a rare study of the MS = –1/2 → MS = +1/2 excitation in transition metal complexes by INS. Indirect‐geometry INS spectrometer VISION has been used to probe the inter‐KD, ZFS transition, MS = ±1/2 (ϕ1,2) → MS = ±3/2 (ϕ3,4) in both 1‐d4 and 1‐d18, by variable‐temperature (VT) properties of this excitation. The INS spectra measured on VISION also give phonon features of the complexes that are well described by periodic DFT phonon calculations. Inelastic Neutron Scattering (INS) has been used to probe intra‐ and inter‐Kramers doublet transitions in Co(acac‐d7)2(D2O)2 (1‐d18) using both variable‐magnetic fields and temperatures. These measurements and INS of Co(acac)2(D2O)2 (1‐d4), coupled with periodic DFT phonon calculations, help reveal magnetic and vibrational properties of the single‐molecule magnets (SMMs). [ABSTRACT FROM AUTHOR]

Neutron diffraction and spectroscopy offer unique insight into structures and properties of solids and molecular materials. All neutron instruments located at the various neutron sources are distinct, even if their designs are based on similar principles, and thus, they are usually less familiar to the community than commercial X-ray diffractometers and optical spectrometers. Major neutron instruments in the USA, which are open to scientists around the world, and examples of their use in coordination chemistry research are presented here, along with a list of similar instruments at main neutron facilities in other countries. The reader may easily and quickly find from this minireview an appropriate neutron instrument for research. The instruments include single-crystal and powder diffractometers to determine structures, inelastic neutron scattering (INS) spectrometers to probe magnetic and vibrational excitations, and quasielastic neutron scattering (QENS) spectrometers to study molecular dynamics such as methyl rotation on ligands. Key and unique features of the diffraction and neutron spectroscopy that are relevant to inorganic chemistry are reviewed.

Co(acac) 2 (H 2 O) 2 ( 1 , acac = acetylacetonate), a transition metal complex ( S   =   3 / 2 ), displays field-induced slow magnetic relaxation as a single-molecule magnet. For 1 and its isotopologues Co(acac) 2 (D 2 O) 2 ( 1- d 4 ) and Co(acac- d 7 ) 2 (D 2 ) in approximately D 4 h symmetry, zero-field splitting of the ground electronic state leads to two Kramers doublets (KDs): lower energy M S   =   ± 1 / 2   ϕ 1 , 2 and higher energy M S   =   ± 3 / 2   ϕ 3 , 4 states. This work employs inelastic neutron scattering (INS), a unique method to probe magnetic transitions, to probe different magnetic excitations in 2 ( 1- d . Direct-geometry, time-of-flight Disk-Chopper Spectrometer (DCS), with applied magnetic fields up to 10 T, has been used to study the intra-KD transition as a result of Zeeman splitting, M S   =   - 1 / 2   ϕ 1   →   M S   =   + 1 / 2   ϕ 2 , in 18 . This is a rare study of the M S   =   - 1 / 2   →   M S   =   + 1 / 2 excitation in transition metal complexes by INS. Indirect-geometry INS spectrometer VISION has been used to probe the inter-KD, ZFS transition, M S   =   ± 1 / 2 ϕ 1 , 2   →   M S   =   ± 3 / 2 ( ϕ 3 , 4 ) in both 1- d 4 and 1- d 18 . Direct-geometry, time-of-flight Disk-Chopper Spectrometer (DCS), with applied magnetic fields up to 10 T, has been used to study the intra-KD transition as a result of Zeeman splitting, M S   =   - 1 / 2   ϕ 1   →   M S   =   + 1 / 2   ϕ 2 , in 1- d 18 . This is a rare study of the M S   =   - 1 / 2   →   M S   =   + 1 / 2 excitation in transition metal complexes by INS. Indirect-geometry INS spectrometer VISION has been used to probe the inter-KD, ZFS transition, M S   =   ± 1 / 2 ϕ 1 , 2   →   M S   =   ± 3 / 2 ( ϕ 3 , 4 ) in both 1- d 4 and 1- d 18 , by variable-temperature (VT) properties of this excitation. The INS spectra measured on VISION also give phonon features of the complexes that are well described by periodic DFT phonon calculations.