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The crystal field parameters are determined from first-principles calculations in the [AnIII(DPA)3]3– series, completing previous work on the [LnIII(DPA)3]3– and [AnIV(DPA)3]2– series. The crystal field strength parameter follows the Ln(III) < An(III) < An(IV) trend. The parameters deduced at the orbital level decrease along the series, while J-mixing strongly impacts the many-electron parameters, especially for the Pu(III) complex. We further compile the available data for the three series. In some aspects, An(III) complexes are closer to Ln(III) than to An(IV) complexes with regard to the geometrical structure and bonding descriptors. At the beginning of the series, up to Pu(III), there is a quantitative departure from the free ion, especially for the Pa(III) complex. The magnetic properties of the actinides keep the trends of the lanthanides; in particular, the axial magnetic susceptibility follows Bleaney’s theory qualitatively.

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The present paper reformulates and improves a previously proposed determinant-based second-order multi-reference perturbative formalism. Through a rather simple modification of the energy denominators, this formalism takes into account the interactions between the model space determinants, which are repeated in outer space. The method has been shown to be size-consistent when the model space is a complete active space, which is a severe limit. It is shown here that the completeness of the model space is not necessary to keep this property, provided that the zero-order function satisfies some conditions. For instance, size consistency may be obtained from truncated complete active spaces. It may even be satisfied from Singles and Doubles Configuration Interactions, provided that a coupled electron pair approximation is used in the definition of the model space wave function. The physical content of the method is illustrated by a series of model problems, showing its robustness. A major benefit of the fact that the perturbers are single determinants is the possibility to revise with full flexibility the model-space component of the wave function, i.e., to treat the feedback effect of the dynamic correlation on the valence component of the wave function.

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We report on NMR spectroscopy, CAS based method calculations and X-ray diffraction on An$^V$ and An$^{VI}$ complexes with a neutral and slightly flexible TEDGA ligand. After checking that pNMR shifts mainly arise from pseudo-contact interactions, pNMR shifts have been analyzed considering axial and rhombic anisotropy of the actinyl magnetic susceptibilities. Results are compared to a previous study performed on [An $^{VI}$O$_2$]$^{2+}$ complexes with dipicolinic acid (DPA). It is shown that 5f$^2$ cations (Pu$^{VI}$ and Np$^V$) make very good candidates to obtain the structure of actinyl complexes in solution by $^1$H NMR spectroscopy as shown by the invariance of the magnetic properties to the equatorial ligands, conversely to the Np$^{VI}$ complexes with a 5f$^1$ configuration.

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Each enantiomer of a chiral pentagonal bipyramidal (PBP) FeII complex ([FeLN5R,RCl(MeOH)]Cl·H2O, 1R, or [FeLN5S,SCl(MeOH)]Cl·H2O, 1S) has been obtained using either the R or the S stereoisomer of the macrocyclic pentadentate ligand formed in a template-condensation reaction of the tetraamine N,N′-Bis-{(1R,2R)-[2-(amino)]cyclohexyl}-1,2-diaminoethane, or its (1S,2S) enantiomer, and 2,5-diacetylpyridine, respectively LN5R,R and LN5S,S. Subsequently, the 1-D coordination polymers [FeLN5R,R{FeCl4}], 2R, and [FeLN5S,S{FeCl4}], 2S, were formed by reacting respectively 1R or 1S with 1 equiv of FeCl2(H2O)4. These chain compounds consist of an alternation of PBP and tetrahedral FeII units sharing a Cl atom. Theoretical calculations reveal large magnetic anisotropy for each Fe center but of different type with axial zero-field splitting parameter D of respectively −30 cm–1 and 15 cm–1. The magnetic behavior for the 1-D compound revealed canted antiferromagnetic Fe–Fe interactions (J = −6 cm–1) and SCM behavior characterized by Δ/kB = 42 K with pre-exponential factor τ0 = 2.17 × 10–10 s. It was noted that this SCM behavior was accompanied by a magnetic order leading to a weak ferromagnet (i.e., canted antiferromagnet). The preparations, crystal structures (CCDC references 2214580–2214583), spectroscopic data, magnetic behaviors, and theoretical investigations are reported.

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A pentadentate-[N3O2] ligand, H2LNMe2, formed by condensation of diacetyl pyridine and dimethylcarbamoyl hydrazide (i. e. Me2NCONHNH2), is reported to yield mononuclear pentagonal bipyramidal (PBP) metal complexes with CrIII, MnII, FeII, CoII, and NiII, that exhibit good solubility in a wide range of solvents as compared to the classically used H2LR ligands. With CuII, dinuclear complexes were obtained. The potassium salt of the deprotonated ligand, K2LNMe2, was also characterized. The reported complexes consist of [CrH2LNMe2Cl2] ⋅ Cl; Cat[CrLNMe2(CN)2] (Cat=K+ or PNP+); [MH2LNMe2(H2O)2] ⋅ (ClO4)2 with M=MnII, CoII, or NiII; [FeH2LNMe2(MeCN)2] ⋅ (PF6)2 ⋅ MeCN; [FeH2LNMe2(MeOH)X] ⋅ X (X=Br or I); [{CuH2LNMe2}2(MeOH)(ClO4)] ⋅ (ClO4)3 ⋅ 1H2O⋅1.75H2O; [CuHLNMe2]2 ⋅ (ClO4)2 ⋅ H2O; and [CuH2LNMe2(H2O)]2 ⋅ (ClO4)4 ⋅ 5H2O. The magnetic behaviors of the PBP derivatives were assessed, especially the zero-field splitting (ZFS) characteristics for the CrIII, FeII, CoII, and NiII derivatives. The ZFS characteristics were also determined from ab initio theoretical calculations. The obtained values confirm those extracted from magnetic measurements.

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Subjets

Model hamiltonian Magnetic anisotropy Electron g-factor Configuration interactions Bleaney Manganites Ab initio calculations Nuclear spin Anisotropie magnétique Ab initio calculation Calculs ab initio Magneto-resistive effects Potential energy surfaces MECHANISM Lanthanides Pentagonal bipyramid Imidazolium salt Calcul ab initio Relativistic and correlated ab initio calculations Molecule-photon collisions NMR MACROCYCLIC POLYARYLMETHYL POLYRADICALS HIGH-SPIN Basis sets Actinide Crystal-field theory and spin Hamiltonians Excitation energies Heptacoordination Molécules aimants Anderson mechanism Negative ions Hyperfine structure Polarization Paramètres du champ cristallin High pressure Coupled cluster calculations Iodine Determinants Ionic liquid Excited states Bleaney's theory Luminescence Polyoxometalates Paramagnetic NMR spectroscopy Magnetic properties Peacock-Weakley Magnetism in organic systems Density functional theory Diagonalisations exactes Lanthanide Décontamination de spin Pentagonal bipyramidal AB-INITIO Heavy fermions Ground states Méthodes basées sur la fonction d’onde Free radicals Double exchange model Actinides Paramagnetism Ligand-field theory Exchange and superexchange interactions Magnétisme dans les systèmes organiques Exact diagonalization Electronic correlation Anisotropy Electron spin Divalent cobalt Paramagnetic chemical shifts Déplacements chimiques paramagnétiques Magnetism MOLECULAR MAGNETIC-MATERIALS Photodissociation Modèle de double échange Covalency Bleaney's model Molecular electronic states Perturbation theory Complexes de métaux de transition Electron paramagnetic resonance Magnétisme moléculaire POLYMER Wave functions Modèle de Bleaney Molecular magnet Spin-orbit interactions NO ligands Crystal field theory Configuration interaction Electron paramagnetism Hyperfine coupling Molecular magnetism Relativistic corrections Calculs ab initio relativistes et corrélés Cooperative effect Effets magnéto-résistifs Hamiltonien modèle Crystal field parameters CLUSTERS Finite nucleus effects

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