Metal-ligand pair anisotropy in a series of mononuclear Er-COT complexes.

Synthetic control of the crystal field has elevated lanthanides to the forefront of single-molecule magnet (SMM) research, yet the resultant strong, predictable single-ion anisotropy has thus far not translated into equally impressive molecule-based magnets of higher dimensionality. This roadblock arises from the dual demands made of the crystal field: generate anisotropy and facilitate magnetic coupling. Here we demonstrate that particular metal-ligand pairs can dominate the single-ion electronic structure so fully that the remaining coordination sphere plays a minimal role in the magnitude and orientation of the magnetic anisotropy. This Metal-Ligand Pair Anisotropy (MLPA) effectively separates the crystal field into discrete components dedicated to anisotropy and magnetic coupling. To demonstrate an MLPA building unit, we synthesized four new mononuclear complexes that challenge the electronic structure of the iconic lanthanocene ([Ln(COT)2]+; COT2- = cyclooctatetraene dianion) complex which is known to generate strong anisotropy with Ln = Er3+. Variation in symmetry and coordination strength for Er(COT)I(THF)2 (THF = tetrahydrofuran) (1), Er(COT)I(Py)2 (Py = pyridine) (2), Er(COT)I(MeCN)2 (MeCN = acetonitrile) (3), and Er(COT)(Tp*) (Tp* = tris(3,5-dimethyl-1-pyrazolyl)borate) (4) shows that the Er-COT unit stabilizes anisotropy despite deliberate de-optimization. All four half-sandwich complexes display SMM behavior with effective energy barriers of U eff = 95.6(9), 102.9(3.1), 107.1(1.3), and 133.6(2.2) cm-1 for 1-4 by a multi-relaxation-process fitting. More importantly, the basic state splittings remain intact and the anisotropy axes are within several degrees of normal to the COT2- ring according to complete active space self-consistent field (CASSCF) calculations. Further investigation of the MLPA conceptual framework is warranted as it can provide building units with well-defined magnetic orientation and strength. We envision that the through-barrier processes observed herein, such as quantum tunneling, can be mitigated by formation of larger clusters and molecule-based materials

Invasive thyroglossal duct cyst papillary carcinoma: a case report

<p>Abstract</p> <p>Introduction</p> <p>A thyroglossal duct cyst is the most common congenital anomaly of the thyroid gland and midline masses in childhood (70% abnormality in childhood, 7% in adult). Carcinomas arising from a thyroglossal duct cyst are rare (only 1% of thyroglossal duct cyst cases) and characterized by relatively non-aggressive behavior and rare lymphatic spread. They are also diagnosed mostly during the third and fourth decades of life. About 85% to 92% of all thyroglossal duct cyst carcinomas are papillary carcinomas.</p> <p>Case presentation</p> <p>We present the case of a 44-year-old Iranian woman with Cacausian ethnicity with a painless anterior neck mass that appeared gradually over three months. She had a history of frequent painful swelling of the anterior part of her neck, which subsided with antibiotic therapy. Thyroid functional tests were normal and a thyroid scinitigraphy showed a cold nodule in the left lobe of her thyroid. A computed tomography scan revealed a large, heterogeneous enhancing soft tissue mass with cystic components in the midline of the anterior neck space. This extended from the base of the tongue,(completely separated from its muscles, to the inferior aspect of the thyroid gland and showed the destruction of the hyoid bone and the thyroid cartilage. The diagnosis of a thyroglossal duct cyst with malignant transformation was maintained. A fine needle aspiration revealed papillary carcinoma.</p> <p>Conclusion</p> <p>This patient's case is presented because of its rare, aggressive, and invasive nature and rare and unusual manifestation, as well as its rapid increase in size, the destruction of the hyoid bone, chondrolysis of the thyroid cartilage, lymph adenopathy and the existence of a cold nodule in the thyroid gland.</p

Size-Controlled Hapticity Switching in [Ln(C9H9)(C8H8)][Ln(C_{9}H_{9})(C_{8}H_{8})] Sandwiches

Sandwich complexes of lanthanides have recently attracted a considerable amount of interest due to their applications as Single Molecule Magnet (SMM). Herein, a comprehensive series of heteroleptic lanthanide sandwich complexes ligated by the cyclononatetraenyl (Cnt) and the cyclooctatetraenyl (Cot) ligand [Ln(Cot)(Cnt)] (Ln=Tb, Dy, Er, Ho, Yb, and Lu) is reported. The coordination behavior of the Cnt ligand has been investigated along the series and shows different coordination patterns in the solid-state depending on the size of the corresponding lanthanide ion without altering its overall anisotropy. Besides the characterization in the solid state by single-crystal X-ray diffraction and in solution by $^{1}H$NMR, static magnetic studies and ab initio computational studies were performed

Metal-ligand pair anisotropy of the erbium-cyclooctatetraenide motif

A magnetostructural study on the erbium–cyclooctatetraenide (Er–COT) motif was conducted. This molecular fragment was shown to generate magnetic anisotropy, and consequently slow magnetic relaxation, in a series of example coordination complexes. The generality of this effect led to creation of the idea that certain metal-ligand pairs can act as magnetic synthons toward the development of single-molecule and molecular magnets. Chapter 1 provides a brief introduction to the study of single-molecule magnetism. It includes a discussion on the historical development of the field, as well as some of the basic theoretical framework required to understand magnetic relaxation on a molecular level. The chapter concludes with the motivation for and introduction of the metal-ligand pair anisotropy design (MLPA) principle.Chapter 2 discusses the development of a technique for measuring the magnetic relaxation time. Relaxation time measurements have historically been carried out using two separate approaches depending on the timescale being studied. A new impedance-based method toward measuring a system's relaxation dynamics at the long timescale is presented which obviates the necessity of two separate measurement approaches.Chapter 3 presents the results of a magnetostructural study conducted on a series of mononuclear Er–COT complexes. A combined magnetic and computational evaluation of Er(COT)I(THF)₂, Er(COT)I(Py)₂, Er(COT)I(MeCN)₂, and Er(COT)(Tp*) (THF = tetrahydrofuran, Py = pyridine, MeCN = acetonitrile, Tp* = tris(3,5-dimethyl-1-pyrazolyl)borate) reveal that each behave as a single-molecule magnet and thus a degree of coordinative robustness within the Er–COT metal-ligand pair is evinced. Chapter 4 introduces the idea of coupling Er–COT units. Therein a dinuclear erbium complex, [Er(COT)(μ-Cl)(THF)]₂, is shown to display a net-ferromagnetic interaction between metal centers while also maintaining magnetic anisotropy. A brief discussion is given on the relevance of this result toward making higher-order structures.Chapter 5 discusses the results of a magnetic coupling optimization study performed on a series of structurally similar MLPA compounds. Mononuclear Er(COT)I(DMPE) (DMPE = 1,2-bis(dimethylphosphino)ethane), and dinuclear [Er(COT)(μ-I)]₂(μ-DPPE), [Er(COT)(μ-I)]₂(μ-DPPM), and [Er(COT)(μ-I)(MDPP)]₂ (DPPE = 1,2-bis(diphenylphosphino)ethane, DPPM = bis(diphenylphosphino)methane, MDPP = methyldiphenylphosphine) were prepared. The effects of nuclearity and anisotropy axis orientation on the low-temperature relaxation time resulted in a million-fold improvement across this series

Metal-ligand pair anisotropy of the erbium-cyclooctatetraenide motif

A magnetostructural study on the erbium–cyclooctatetraenide (Er–COT) motif was conducted. This molecular fragment was shown to generate magnetic anisotropy, and consequently slow magnetic relaxation, in a series of example coordination complexes. The generality of this effect led to creation of the idea that certain metal-ligand pairs can act as magnetic synthons toward the development of single-molecule and molecular magnets. Chapter 1 provides a brief introduction to the study of single-molecule magnetism. It includes a discussion on the historical development of the field, as well as some of the basic theoretical framework required to understand magnetic relaxation on a molecular level. The chapter concludes with the motivation for and introduction of the metal-ligand pair anisotropy design (MLPA) principle.Chapter 2 discusses the development of a technique for measuring the magnetic relaxation time. Relaxation time measurements have historically been carried out using two separate approaches depending on the timescale being studied. A new impedance-based method toward measuring a system's relaxation dynamics at the long timescale is presented which obviates the necessity of two separate measurement approaches.Chapter 3 presents the results of a magnetostructural study conducted on a series of mononuclear Er–COT complexes. A combined magnetic and computational evaluation of Er(COT)I(THF)₂, Er(COT)I(Py)₂, Er(COT)I(MeCN)₂, and Er(COT)(Tp*) (THF = tetrahydrofuran, Py = pyridine, MeCN = acetonitrile, Tp* = tris(3,5-dimethyl-1-pyrazolyl)borate) reveal that each behave as a single-molecule magnet and thus a degree of coordinative robustness within the Er–COT metal-ligand pair is evinced. Chapter 4 introduces the idea of coupling Er–COT units. Therein a dinuclear erbium complex, [Er(COT)(μ-Cl)(THF)]₂, is shown to display a net-ferromagnetic interaction between metal centers while also maintaining magnetic anisotropy. A brief discussion is given on the relevance of this result toward making higher-order structures.Chapter 5 discusses the results of a magnetic coupling optimization study performed on a series of structurally similar MLPA compounds. Mononuclear Er(COT)I(DMPE) (DMPE = 1,2-bis(dimethylphosphino)ethane), and dinuclear [Er(COT)(μ-I)]₂(μ-DPPE), [Er(COT)(μ-I)]₂(μ-DPPM), and [Er(COT)(μ-I)(MDPP)]₂ (DPPE = 1,2-bis(diphenylphosphino)ethane, DPPM = bis(diphenylphosphino)methane, MDPP = methyldiphenylphosphine) were prepared. The effects of nuclearity and anisotropy axis orientation on the low-temperature relaxation time resulted in a million-fold improvement across this series

Madame de Maintenon et le duc du Maine

Hilgar Marie-France. Madame de Maintenon et le duc du Maine. In: Albineana, Cahiers d'Aubigné, 10-11, 1999. Autour de Françoise d’Aubigné, Marquise de Maintenon. Tome II. Actes des Journées de Niort 23-25 mai 1996, sous la direction de Alain Niderst . pp. 259-267