Martin Novák

Supramolecular Covalence in Bifurcated Chalcogen Bonding

Supramolecular interactions are generally classified as noncovalent. However, recent studies have demonstrated that many of these interactions are stabilized by a significant covalent component. Herein, for systems of the general structure [MX6 ]2- :YX2 (M=Se or Pt; Y=S, Se, or Te; X=F, Cl, Br, I), featuring bifurcated chalcogen bonding, it is shown that, although electrostatic parameters are useful for estimating the long-range electrostatic component of the interaction, they fail to predict the correct order of binding energies in a series of compounds. Instead, the Lewis basicity of the individual substituents X on the chalcogen atom governs the trends in the binding energies through fine-tuning the covalent character of the chalcogen bond. The effects of substituents on the binding energy and supramolecular electron sharing are consistently identified by an arsenal of theoretical methods, ranging from approaches based on the quantum chemical topology to analytical tools based on the localized molecular orbitals. The chalcogen bonding investigated herein is driven by orbital interactions with significant electron sharing; this can be designated as supramolecular covalence.

Modulating Electron Sharing in Ion-π-Receptors via Substitution and External Electric Field: A Route toward Bond Strengthening.

Substituted coronenes, a family of ion-π receptors whose ion-affinities can be explained exclusively neither via ion-quadrupole nor induction/polarization mechanisms, are studied. The best descriptors of ion-affinity among these species are those characterizing charge-transfer between ions and the π-systems, e.g. vertical ionization potential, electron affinity, and the relative energies of charge-transfer excited-states (CTESs). The variation of the electric multipole moments, polarizability, binding energy, and relative energy of CTESs in the presence of an external electric field (EEF) is evaluated. The results indicate that the EEF has a negligible effect on the polarizability and quadrupole moment of the systems. However, it significantly affects the binding energies, CTES energies, and the dipole moments of the receptors. Contrary to the changes in the dipole moment, the variation pattern of the binding energy is more consistent with the pattern observed for the CTES energy changes. Finally, by analyzing the exchange-correlation component of the binding energy we demonstrate that the increased binding energy, i.e. bond strengthening, originates from enhanced electron sharing and multicenter covalency between the ions and the π-systems as a result of the state-mixing between the ground-state and the CTESs. According to our findings, we hypothesize that the electron sharing and in extreme cases the multicenter covalency are the main driving forces for complexation of ions with extended π-receptors such as carbon nanostructures.

Solvent effects on ion–receptor interactions in the presence of an external electric field

In this work we investigated the influence of an external electric field on the arrangement of the solvent shells around ions interacting with a carbon-based receptor. Our survey reveals that the mechanism of interaction between a monoatomic ion and a π-type ion receptor varies by the variation in the solvent polarity, the nature of the ion, and the strength of the external field. The characteristics of the ion-surface interaction in nonpolar solvents are similar to those observed in a vacuum. However, in water, we identified two mechanisms. Soft and polarizable ions preferentially interact with the π-receptor. In contrast, two bonded states were found for hard ions. A fully solvated ion, weakly interacting with the receptor at weak field, and a strong π-complex at the strong-field regime were identified. An abrupt variation in the potential energy surface (PES) associated with the rearrangement of the solvation shell on the surface of the receptor induced by an external field was observed both in implicit and explicit solvent environments. The electric field at which the solvation shell breaks is proportional to the hardness of the ion as has been suggested recently based on experimental observations.

Through-Space Paramagnetic NMR Effects in Host–Guest Complexes: Potential Ruthenium(III) Metallodrugs with Macrocyclic Carriers

The potential of paramagnetic ruthenium(III) compounds for use as anticancer metallodrugs has been investigated extensively during the past several decades. However, the means by which these ruthenium compounds are transported and distributed in living bodies remain relatively unexplored. In this work, we prepared several novel ruthenium(III) compounds with the general structure Na+[ trans-RuIIICl4(DMSO)(L)]- (DMSO = dimethyl sulfoxide), where L stands for pyridine or imidazole linked with adamantane, a hydrophobic chemophore. The supramolecular interactions of these compounds with macrocyclic carriers of the cyclodextrin (CD) and cucurbit[ n]uril (CB) families were investigated by NMR spectroscopy, X-ray diffraction analysis, isothermal titration calorimetry, and relativistic DFT methods. The long-range hyperfine NMR effects of the paramagnetic guest on the host macrocycle are related to the distance between them and their relative orientation in the host-guest complex. The CD and CB macrocyclic carriers being studied in this account can be attached to a vector that attracts the drug-carrier system to a specific biological target and our investigation thus introduces a new possibility in the field of targeted delivery of anticancer metallodrugs based on ruthenium(III) compounds.

Ventricular Septal Rupture – A Critical Condition as a Complication of Acute Myocardial Infarction

Abstract Ventricular septal rupture is a potentially fatal complication of acute myocardial infarction. The key to management of this critical condition is an aggressive approach to haemodynamic stabilization and surgical closure of the rupture. Where there is a small rupture and the patient is in a haemodynamically stable condition, surgery can be delayed with the prospect of achieving better perioperative results. However, in unstable critically ill patients either immediate surgery or extracorporeal membranous oxygenation support and delayed surgery is indicated. In some patients, trans-catheter closure may be considered as an alternative to surgery.

Intracoronary Imaging for Assessment of Vascular Healing and Stent Follow-up in Bioresorbable Vascular Scaffolds

Bioresorbable Vascular Scaffolds (BVS) are polymer-based materials implanted in the coronary arteries in order to treat atherosclerotic lesions, based on the concept that once the lesion has been treated, the material of the implanted stent will undergo a process of gradual resorption that will leave, in several years, the vessel wall smooth, free of any foreign material and with its vasomotion restored. However, after the first enthusiastic reports on the efficacy of BVSs, the recently published trials demonstrated disappointing results regarding long-term patency following BVS implantation, which were mainly attributed to technical deficiencies during the stenting procedure. Intracoronary imaging could play a crucial role for helping the operator to correctly implant a BVS into the coronary artery, as well as providing relevant information in the follow-up period. This review aims to summarize the role of intracoronary imaging in the follow-up of coronary stents, with a particular emphasis on the role of intravascular ultrasound and optical coherence tomography for procedural guidance during stent implantation and also for follow-up of bioabsorbable scaffolds.

Anion Recognition by a Bioactive Diureidodecalin Anionophore: Solid-State, Solution, and Computational Studies

Abstract Recent work has identified a bis‐(p‐nitrophenyl)ureidodecalin anion carrier as a promising candidate for biomedical applications, showing good activity for chloride transport in cells yet almost no cytotoxicity. To underpin further development of this and related compounds, a detailed structural and binding investigation is reported. Crystal structures of the transporter as five solvates confirm the diaxial positioning of urea groups while revealing a degree of conformational flexibility. Structures of complexes with Cl−, Br−, NO3 −, SO4 2− and AcO−, supported by computational studies, show how the binding site can adapt to accommodate these anions. 1H NMR binding studies revealed exceptionally high affinities for anions in DMSO, decreasing in the order SO4 2−>H2PO4 −≈HCO3 −≈AcO−≫HSO4 −>Cl−>Br−>NO3 −>I−. Analysis of the binding results suggests that selectivity is determined mainly by the H‐bond acceptor strength of different anions, but is also modulated by receptor geometry.

The First Manifestation of a Left Atrial Myxoma as a Consequence of Multiple Left Coronary Artery Embolisms

Abstract A case of multiple embolisms in the left coronary artery as a rare first manifestation of left atrial myxoma is reported. A patient with embolic myocardial infarction and congestive heart failure was treated by percutaneous aspirations and balloon dilatations. Transesophageal echocardiography disclosed a villous myxoma with high embolic potential. Surgical resection of the tumour, suturing of a patent foramen ovale suture and an annuloplasty of the dilated tricuspid annulus was performed the third day after the admission. Recovery of the documented left ventricular systolic function can be explained by resorption of myxomatous material. The patient was discharged ten days after the surgery.

Anti-Electrostatic CH-Ion Bonding in Decorated Graphanes

State-of-the-art computations combined with Ziegler-Rauk energy decomposition analyses are employed to introduce a new class of anti-electrostatic ion-σ bonds with considerable stability and a substantial contribution from charge transfer and dispersion between ions and finite-size functionalized graphane flakes, G-XYs. G-XYs have diverse electric multipolar moments that are comparable with those of newly synthesized all-cis-hexa-halocyclohexanes. The strong, long-range electrostatic and Pauli repulsions between some G-XYs and certain ions induce a gas-phase energy barrier to the physisorption of ions on the surface of G-XYs. However, the repulsive interactions can be overbalanced by the strong orbital interactions operating in the formation of ion-σ complexes at short range, leading to covalent-type intermolecular bonds as strong as -34 kcal mol-1 .

New Imaging Methods of Coronary Arteries in Acute Coronary Syndromes

Abstract Coronary angiography is still the most widely used method for the assessment of lumen of coronary arteries and for diagnosis and treatment of coronary artery disease. New imaging modalities of coronary arteries play an increasing role in interventional cardiology. Intravascular ultrasound (IVUS) is the oldest technology, however due to its high tissue penetration remains very important for imaging of left main coronary artery and saphenous vein grafts. IVUS was used in many clinical trials and clinical experience with it is huge. Optical coherence tomography (OCT) is a new, very fast developing method. It has ten times higher axial resolution than IVUS. It gives us the opportunity to assess the inner structures of coronary artery wall, to evaluate the characteristics of atherosclerotic plaques, quality of stent implantation and its healing. It helps us to find the culprit lesion of acute coronary syndrome in some cases, to diagnose the cause of stent thrombosis, and to evaluate stent apposition which has a direct relation to prognosis. We use it to perform complex percutaneous coronary interventions and after heart transplantation to diagnose the vascular graft disease. We strongly believe that OCT is important for the assessment of plaque instability and patient´s prognosis. Near infrared spectroscopy combined with IVUS can distinguish fibrous from lipid core plaques. Lipid core burden index is in relation to a risk of periprocedural myocardial infarction and to prognosis. It is the only method which can sufficiently detect the amount of lipids in coronary wall.