Widening the Window of Spin-Crossover Temperatures in Bis(formazanate)iron(II) Complexes via Steric and Noncovalent Interactions

Bis(formazanate)iron(II) complexes undergo a thermally induced S = 0 to S = 2 spin transition in solution. Here we present a study of how steric effects and π-stacking interactions between the triarylformazanate ligands affect the spin-crossover behavior, in addition to electronic substituent effects. Moreover, the effect of increasing the denticity of the formazanate ligands is explored by including additional OMe donors in the ligand (7). In total, six new compounds (2-7) have been synthesized and characterized, both in solution and in the solid state, via spectroscopic, magnetic, and structural analyses. The series spans a broad range of spin-crossover temperatures (T1/2) for the LS ⇌ HS equilibrium in solution, with the exception of compound 6 which remains high-spin (S = 2) down to 210 K. In the solid state, 6 was shown to exist in two distinct forms: a tetrahedral high-spin complex (6a, S = 2) and a rare square-planar structure with an intermediate-spin state (6b, S = 1). SQUID measurements, 57Fe Mössbauer spectroscopy, and differential scanning calorimetry indicate that in the solid state the square-planar form 6b undergoes an incomplete spin-change-coupled isomerization to tetrahedral 6a. The complex that contains additional OMe donors (7) results in a six-coordinate (NNO)2Fe coordination geometry, which shifts the spin-crossover to significantly higher temperatures (T1/2 = 444 K). The available experimental and computational data for 7 suggest that the Fe···OMe interaction is retained upon spin-crossover. Despite the difference in coordination environment, the weak OMe donors do not significantly alter the electronic structure or ligand-field splitting, and the occurrence of spin-crossover (similar to the compounds lacking the OMe groups) originates from a large degree of metal-ligand π-covalency

Electronic Control of Spin-Crossover Properties in Four-Coordinate Bis(formazanate) Iron(II) Complexes

The transition between spin states in d-block metal complexes has important ramifications for their structure and reactivity, with applications ranging from information storage materials to understanding catalytic activity of metalloenzymes. Tuning the ligand field (Delta(O)) by steric and/or electronic effects has provided spin-crossover compounds for several transition metals in the periodic table, but this has mostly been limited to coordinatively saturated metal centers in octahedral ligand environments. Spin-crossover complexes with low coordination numbers are much rarer. Here we report a series of four-coordinate, (pseudo)tetrahedral Fe(II) complexes with formazanate ligands and demonstrate how electronic substituent effects can be used to modulate the thermally induced transition between S = 0 and S = 2 spin states in solution. All six compounds undergo spin-crossover in solution with T-1/2 above room temperature (300-368 K). While structural analysis by X-ray crystallography shows that the majority of these compounds are low-spin in the solid state (and remain unchanged upon heating), we find that packing effects can override this preference and give rise to either rigorously high-spin (6) or gradual spin-crossover behavior (5) also in the solid state. Density functional theory calculations are used to delineate the empirical trends in solution spin-crossover thermodynamics. In all cases, the stabilization of the low-spin state is due to the pi-acceptor properties of the formazanate ligand, resulting in an "inverted" ligand field, with an approximate "two-over-three" splitting of the d-orbitals and a high degree of metal-ligand covalency due to metal -> ligand pi-backdonation. The computational data indicate that the electronic nature of the para-substituent has a different influence depending on whether it is present at the C-Ar or N-Ar rings, which is ascribed to the opposing effect on metal-ligand sigma- and pi-bonding

Genetic association study of QT interval highlights role for calcium signaling pathways in myocardial repolarization.

The QT interval, an electrocardiographic measure reflecting myocardial repolarization, is a heritable trait. QT prolongation is a risk factor for ventricular arrhythmias and sudden cardiac death (SCD) and could indicate the presence of the potentially lethal mendelian long-QT syndrome (LQTS). Using a genome-wide association and replication study in up to 100,000 individuals, we identified 35 common variant loci associated with QT interval that collectively explain ∼8-10% of QT-interval variation and highlight the importance of calcium regulation in myocardial repolarization. Rare variant analysis of 6 new QT interval-associated loci in 298 unrelated probands with LQTS identified coding variants not found in controls but of uncertain causality and therefore requiring validation. Several newly identified loci encode proteins that physically interact with other recognized repolarization proteins. Our integration of common variant association, expression and orthogonal protein-protein interaction screens provides new insights into cardiac electrophysiology and identifies new candidate genes for ventricular arrhythmias, LQTS and SCD

CCDC 2036149: Experimental Crystal Structure Determination

Related Article: Francesca Milocco, Folkert de Vries, Harmke S. Siebe, Silène Engbers, Serhiy Demeshko, Franc Meyer, Edwin Otten|2021|Inorg.Chem.|60|2045|doi:10.1021/acs.inorgchem.0c0359

CCDC 2036150: Experimental Crystal Structure Determination

Related Article: Francesca Milocco, Folkert de Vries, Harmke S. Siebe, Silène Engbers, Serhiy Demeshko, Franc Meyer, Edwin Otten|2021|Inorg.Chem.|60|2045|doi:10.1021/acs.inorgchem.0c0359

CCDC 2036151: Experimental Crystal Structure Determination

Related Article: Francesca Milocco, Folkert de Vries, Harmke S. Siebe, Silène Engbers, Serhiy Demeshko, Franc Meyer, Edwin Otten|2021|Inorg.Chem.|60|2045|doi:10.1021/acs.inorgchem.0c0359

CCDC 2036152: Experimental Crystal Structure Determination

Related Article: Francesca Milocco, Folkert de Vries, Harmke S. Siebe, Silène Engbers, Serhiy Demeshko, Franc Meyer, Edwin Otten|2021|Inorg.Chem.|60|2045|doi:10.1021/acs.inorgchem.0c0359

CCDC 2036148: Experimental Crystal Structure Determination

Related Article: Francesca Milocco, Folkert de Vries, Harmke S. Siebe, Silène Engbers, Serhiy Demeshko, Franc Meyer, Edwin Otten|2021|Inorg.Chem.|60|2045|doi:10.1021/acs.inorgchem.0c0359

The Erlangen Glaucoma Registry: a Scientific Database for Longitudinal Analysis of Glaucoma

Background: Due to the slow progression of the Glaucoma disease, a large study population and long-time observations are needed to gain insights into its long-term effects and progression rates. Since modalities can export data in machine-readable formats, statistical analyses of the large number of examinations is feasible. These data have been integrated in a central patient registry, the Erlangen Glaucoma Registry (EGR). Objectives: The primary focus of the EGR system design has been its fitness for analyses. It holds almost all the available research data for registered glaucoma patients. This allows for cross-sectional and longitudinal observations and for evaluation of prognostic validity of diagnostic procedures. Methods: An adequate technology for integration of data and flexibility in data analysis is a database management system (DBMS). Here, a careful schema design is mandatory. Adding new modalities leads to schema modifications which are supported by defining a core database schema and attaching all data to this core. On that basis, a large number of modalities have been connected to the EGR. Results: The registry contains data of 1,400 patients in the main longitudinal study. It has successfully helped in scientific research, as can be seen in a large number of published papers. For example, validation of new sensory physiological methods requires patients with reliable diagnoses. The existence of a well-documented patient collective facilitated finding such patients. Conclusions: The EGR holds a unique amount of available data gathered in large longitudinal studies. It was successful in terms of medical results obtained. Developed as an evolutionary system, it can easily be extended