Phenol-pyrazole ligands in the design of manganese(III) compounds : synthesis, structural characterization and study of the magnetic properties

In this thesis project, new manganese(III) compounds containing phenol-pyrazole ligands are presented. Small variations on the phenol-pyrazole ligand have been performed to investigate the role of the ligand in the formation of new complexes. The reaction conditions are also crucial to determine the nuclearity of the obtained compounds, which range from mononuclear to octanuclear compounds. Additionally, the magnetic properties of the synthesized compounds were studied. Magneto-structural correlations are presented to assess the important structural features for tuning the magnetic properties

Hysteresis in a bimetallic holmium complex : A synergy between electronic and nuclear magnetic interactions

We report a bimetallic holmium(III) complex showing a S-shaped magnetic hysteresis at low temperature. The complex is investigated by x-ray crystallography, magnetometry, single crystal microsquid measurements, and first-principles calculations. A model Hamiltonian including electronic and nuclear magnetic moments is used to fit all experimental data. We conclude that the Ho(III) may be described as non-Kramers doublets with respective gaps of Delta(A) = 0.8 and Delta(B) = 10 cm(-1) and that there is a small ferromagnetic coupling of J = 1 cm(-1) ((H) over cap (S) = -JS(A) . S-B). As in previous works, the hysteresis arise from the hyperfine structure of the Ho(III) ions. The S-shaped form of the hysteresis reflects the avoided crossing of the electronic states in the non-Kramers doublets.Peer reviewe

[Cr(dmbipy)(ox)2]−: a new bis-oxalato building block for metal assembling. Crystal structures and magnetic properties of XPh4[Cr(dmbipy)(ox)2]·5H2O (X = P and As), {Ba(H2O)2[Cr(dmbipy)(ox)2]2}n·17/2nH2O and {Ag(H2O)[Cr(dmbipy)(ox)2]}n·3nH2O

The synthesis, X-ray structure and variable-temperature magnetic study of new compounds of formula PPh4 [Cr(dmbipy)(ox)2 ]$5H2O (1), AsPh4 [Cr(dmbipy)(ox)2 ]$5H2O (2), {Ba(H2O)2[Cr(dmbipy)(ox)2]2}n$17/2nH2O (3) and {Ag(H2O)[Cr(dmbipy)(ox)2]}n$3nH2O (4) (PPh4 + ¼ tetraphenylphosphonium cation; AsPh4 + ¼ tetraphenylarsonium cation; dmbipy ¼ 4,4 0 -dimethyl- 2,2 0 -bipyridine; ox 2 ¼ oxalate dianion) are reported herein. The isomorphous compounds 1 and 2 are made up of discrete [Cr(dmbipy)(ox)2] anions, XPh4 + cations [X ¼ P (1) and As (2)] and uncoordinated water molecules. The chromium environment in 1 and 2 is distorted octahedral with Cr–O and Cr–N bond distances varying in the ranges 1.950(2)–1.9782(12) and 2.047(3)–2.0567(14) A˚ , respectively. The angles subtended at the chromium atom by the two bidentate oxalate ligands cover the range 82.58(10)– 83.11(5) , and they are somewhat greater than those concerning the chelating dmbipy [79.04(10) (1) and 79.24(5) (2)]. The [Cr(dmbipy)(ox)2] unit of 1 and 2 also occurs in 3 and 4 but it adopts different coordination modes. It acts as a chelating ligand through its two oxalate groups towards the divalent barium cations in 3 affording neutral chains with diamond-shaped units sharing the barium atoms, while the two other corners are occupied by two crystallographically independent chromium atoms. The barium atom in 3 is coordinated by eight oxygen atoms from four oxalate groups and two aqua ligands. The structure of 4 consists of neutral bimetallic layers where the [Cr(dmbipy)(ox)2] unit acts as a ligand towards the univalent silver(I) cation through its two oxalate groups, one of them being bidentate and the other bidentate/monodentate (outer). Each silver atom is six-coordinated with a water molecule and five oxygen atoms from three oxalate groups building a highly distorted octahedral environment. Magnetic susceptibility measurements for 1–4 in the temperature range 1.9– 300 K show the occurrence of weak ferro- (1 and 2) and antiferromagnetic (3 and 4) interactions which are mediated by p–p stacking between dmbipy ligands through the spin polarization mechanism. A comparative study of the potentiality of the [Cr(AA)(ox)2] unit (AA ¼ bidentate nitrogen donor) as a building bl

Functionalisation of MoS2 2D layers with diarylethene molecules

Functionalisation of two dimensional (2D) materials with stimuli-responsive molecules has been scarcely investigated. Here, MoS2 layers obtained by chemical exfoliation are covalently and non-covalently functionalised using two photoswitchable diarylethene derivatives under their open- and closed-ring isomers. The choice of these light-responsive molecules is based on their excellent thermal irreversibility and fatigue resistance. The characterisation of the resultant molecular/2D heterostructures proves the successful anchoring of the molecules by both approaches as well as the influence that the driving interaction has in the photoswitching behaviour of the diarylethene isomers after their deposition on the 2D layer

Compact Hydrogen-Bonded Self-Assembly of Ni(II)−Salen Derivative Investigated Using Scanning Tunneling Microscopy

International audienceThe self-assembly of a Ni(II)−salen-derived complex bearing benzoate groups is investigated using scanning tunneling microscopy (STM) at the solid/liquid interface. STM reveals that the molecules form a two-dimensional nanoarchitecture of close-packed hydrogen-bonded chains on graphite surface. Favorable salen chain-shaped complementarity and molecular dipolar interactions appear to be at the origin of the compact molecular chain-packing

Compact Hydrogen-Bonded Self-Assembly of Ni(II)–Salen Derivative Investigated Using Scanning Tunneling Microscopy

The self-assembly of a Ni­(II)–salen-derived complex bearing benzoate groups is investigated using scanning tunneling microscopy (STM) at the solid/liquid interface. STM reveals that the molecules form a two-dimensional nanoarchitecture of close-packed hydrogen-bonded chains on graphite surface. Favorable salen chain-shaped complementarity and molecular dipolar interactions appear to be at the origin of the compact molecular chain-packing

Photodegradation of Brilliant Green Dye by a Zinc bioMOF and Crystallographic Visualization of Resulting CO2

We present a novel bio-friendly water-stable Zn-based MOF (1), derived from the natural amino acid L-serine, which was able to efficiently photodegrade water solutions of brilliant green dye in only 120 min. The total degradation was followed by UV-Vis spectroscopy and further confirmed by single-crystal X-ray crystallography, revealing the presence of CO2 within its channels. Reusability studies further demonstrate the structural and performance robustness of 1