Uncovering Factors Controlling Reactivity of Metal-TEMPO Reaction Systems in the Solid State and Solution.

Nitroxides find application in various areas of chemistry, and a more in-depth understanding of factors controlling their reactivity with metal complexes is warranted to promote further developments. Here, we report on the effect of the metal centre Lewis acidity on both the distribution of the O- and N-centered spin density in 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) and turning TEMPO from the O- to N-radical mode scavenger in metal-TEMPO systems. We use Et(Cl)Zn/TEMPO model reaction system with tuneable reactivity in the solid state and solution. Among various products, a unique Lewis acid-base adduct of Cl2Zn with the N-ethylated TEMPO was isolated and structurally characterised, and the so-called solid-state 'slow chemistry' reaction led to a higher yield of the N-alkylated product. The revealed structure-activity/selectivity correlations are exceptional yet are entirely rationalised by the mechanistic underpinning supported by theoretical calculations of studied model systems. This work lays a foundation and mechanistic blueprint for future metal/nitroxide systems exploration.

Atrial Septum Perforation Via Levoatriocardinal Vein in a Newborn With Hypoplastic Left Heart Syndrome.

Hypoplastic left heart syndrome with intact atrial septum has high perioperative mortality. An interventional septum perforation from the right atrium may be technically challenging in newborns with high risk of tamponade. However, neonates with a levoatriocardinal vein provide an alternative approach for septostomy from the left atrium side. (Level of Difficulty: Advanced.).

Coronary steal phenomenon following right ventricle decompression and revascularization of atretic left coronary ostium: case report.

BACKGROUND: Coronary steal phenomenon and myocardial ischemia is a complication following decompression of a hypertensive right ventricle in patients with left coronary-cameral fistulae. CASE PRESENTATION: We present a 12-year-old girl with a complex heart defect successfully operated on using a hybrid surgical-interventional approach to decompress the ventricle, embolize the fistula and reconstruct the atretic left coronary ostium. CONCLUSIONS: A novel hybrid strategy is the best solution for coronary-cameral fistulas reliant on high ventricular pressure at high risk for coronary steal phenomenon.

A Case Study on the Desired Selectivity in Solid-State Mechano- and Slow-Chemistry, Melt, and Solution Methodologies.

Solution-based syntheses are omnipresent in chemistry but are often associated with obvious disadvantages, and the search for new mild and green synthetic methods continues to be a hot topic. Here, comparative studies in four different reaction media were conducted, that is, the solid-state mechano- and slow-chemistry synthesis, melted phase, and solution protocols, and the impact of the employed solvent-free solid-state versus liquid-phase synthetic approaches was highlighted on a pool of products. A moderately exothermic model reaction system was chosen based on bis(pentafluorophenyl)zinc, (C6 F5 )2 Zn, and 2,2,6,6-tetramethylpiperidinyl oxide (TEMPO) as a stable nitroxyl radical, anticipating that these reagents may offer a unique landscape for addressing kinetic and thermodynamic aspects of wet and solvent-free solid-state processes. In a toluene solution two distinct paramagnetic Lewis acid-base adducts (C6 F5 )2 Zn(η1 -TEMPO) (1) and (C6 F5 )2 Zn(η1 -TEMPO)2 (2) equilibrated, but only 2 was affordable by crystallization. In turn, crystallization from the melt was the only method yielding single crystals of 1. Moreover, the solid-state approaches were stoichiometry sensitive and allowed for the selective synthesis of both adducts by simple stoichiometric control over the substrates. Density functional theory (DFT) calculations were carried out to examine selected structural and thermodynamic features of the adducts 1 and 2. Compound 2 is a unique non-redox active metal complex supported by two nitroxide radicals, and the magnetic studies revealed weak-to-moderate intramolecular antiferromagnetic interactions between the two coordinated TEMPO molecules.

Left ventricular systolic function impairment in children after balloon valvuloplasty for congenital aortic stenosis assessed by 2D speckle tracking echocardiography.

AIMS: The aim of the study was to evaluate left ventricular (LV) remodeling and systolic function using two-dimensional speckle tracking echocardiographic (2D STE) imaging in children at a long-term (more than 36 months, 107.5±57.8 months) after balloon valvuloplasty for aortic stenosis (BAV). METHODS AND RESULTS: 40 patients (mean age 9,68 years, 75% male) after BAV and 62 control subjects matched to the age and heart rate were prospectively evaluated. The 2D STE assessment of LV longitudinal and circumferential strain and strain rate was performed. Left ventricular eccentric hypertrophy (LVEH) was diagnosed in 75% of patients in the study group. Left ventricular ejection fraction (LVEF) was normal in all patients. In study group, global longitudinal strain (GLS), global longitudinal strain rate (GLSr) were significantly lower compared with the controls: GLS (-19.7±2.22% vs. -22.3±1.5%, P< 0.001), GLSr (-0.89±0.15/s vs. -1.04 ±0.12/s, P < 0.001). Regional (basal, middle and apical segments) strain and strain rate were also lower compared with control group. Global circumferential strain (GCS), global circumferential strain rate (GCSr) as well as regional (basal, middle and apical segments) strain and strain rate were normal. Multivariable logistic regression analysis included: instantaneous peak systolic Doppler gradient across aortic valve (PGmax), grade of aortic regurgitation (AR), left ventricular mass index (LVMI), left ventricular relative wall thickness (LVRWT), left ventricular end-diastolic diameter (LVEDd), peak systolic mitral annular velocity of the septal and lateral corner (S'spt, S'lat), LVEF before BAV and time after BAV and showed that the only predictor of reduced GLS was LV eccentric hypertrophy [odds ratio 6.9; (95% CI: 1.37-12.5), P = 0.045]. CONCLUSION: Patients at long-term observation after BAV present the subclinical LV systolic impairment, which is associated with the presence of its remodeling. Longitudinal deformation is the most sensitive marker of LV systolic impairment in this group of patients.

Long-term results of percutaneous balloon aortic valvuloplasty in children with aortic stenosis: a single-center experience.

BACKGROUND: Percutaneous balloon aortic valvuloplasty (BAV) is an effective method of treatment for aortic stenosis in children. AIMS: This study aimed to assess the long­term results of BAV in various age groups in the pediatric population. METHODS: This retrospective study included 68 patients (newborns, infants, and children older than 1 year). We analyzed their demographic data and measurements performed with the use of cardiac catheterization, angiography, and echocardiography at 3 time points: before, directly after, and at late follow­up after BAV, including the invasive aortic valve peak­to­peak systolic pressure gradient (PGpeak), maximum systolic pressure gradient (PGmax) by Doppler echocardiography, and the severity of aortic regurgitation (AR). Long­­term follow­up data were available for 57 patients. RESULTS: The BAV procedure led to a significant reduction in the PGpeak values. Late follow­up revealed a progression of AR. Aortic regurgitation of grade 2 or higher directly after BAV was the strongest risk factor for severe AR at late follow­up. After 5, 10, and 18 years after BAV, surgical treatment was not required in 90%, 77%, and 59.5% of patients, respectively. Severe AR and a residual PG less than 35 mm Hg at late follow­up were stronger risk factors for aortic valve surgery than moderate AR and PG higher than or equal to 35 mm Hg. CONCLUSIONS: Balloon aortic valvuloplasty is an effective method of treatment for aortic stenosis in children, which delays the need for surgery. The progression of AR occurs at late follow­up. A greater reduction in PGmax is a risk factor for at least moderate AR directly after BAV, which results in the progression of AR at late follow­up.

Mechanochemical and slow-chemistry radical transformations: a case of diorganozinc compounds and TEMPO.

From the green chemistry perspective, molecular solid-state transformations conducted under mild conditions are of great interest and desirability. However, research in this area lacked popularity in the previous century, and thus progressed slowly. In particular, the application of radical reactions in solid-state chemistry has been hampered by several long-standing challenges that are intrinsically associated with the apparent unpredictable nature of radical chemistry. We present a comparative study of model mechanochemical, slow-chemistry and solution radical reactions between TEMPO and homoleptic organozinc compounds (i.e., di-tert-butylzinc and diphenylzinc). In the case of the tBu2Zn/TEMPO reaction system only a dimeric diamagnetic complex [tBuZn(µ-TEMPO*)]2 is obtained in yields slightly varying with the method chosen. In contrast, when TEMPO is mixed with diphenylzinc in a 2 : 1 molar ratio a novel paramagnetic Lewis acid-base adduct [[Ph2Zn(η1-TEMPO)]·TEMPO] is isolated in high yields regardless of the applied methodology. This adduct is also formed in the slow-chemistry process when TEMPO is gently mixed with Ph2Zn in a 1 : 1 molar ratio and left for two weeks at ambient temperature. Within the next week the reaction mixture gives in high yield a diamagnetic dinuclear compound [PhZn(µ-TEMPO*)][PhZn(µ2-η1:η1-TEMPO*)] and biphenyl. The analogous reaction conducted in toluene results in a much lower conversion rate. The reported results open up a new horizon in molecular solid-state radical transformations.

Development of zinc alkyl/air systems as radical initiators for organic reactions.

This paper reports a series of comparative experiments on the activity of carbon- and oxygen-centred radical species in a model reaction of the radical addition of THF to imines mediated by a series of zinc alkyl/air reaction systems. The study strongly contradicts the notion that generally R˙ radicals are the initiating species in organic reactions mediated by R n M/air systems, and simultaneously demonstrates that oxygen-centred radical species are the key intermediates responsible for the initiation process. In addition, a new efficient RZn(L)/air initiating system for radical organic reactions exampled by a model reaction of radical addition of THF to imines is developed. Moreover, the isolation and structural characterization of the first zinc alkylperoxide supported by a carboxylate ligand, [Zn4(µ3-OOtBu)3(µ4-O)(O2CEt)3]2, as well as the novel octanuclear zinc oxo(alkoxide) aggregate with entrapped O-THF species, [Zn4(µ4-O)(µ3-2-O-THF)(O2CEt)5]2, provide clear mechanistic signatures for the mode of function of the RZn(O2CR')/air system.

[Myocardial infarction after butane inhalation in a 14-year-old boy]. / Zawal serca u 14-letniego chlopca po inhalacji butanu.

Myocardial infarction is a rare disease in children. Among many reasons the toxic damage of myocardium should be taken into consideration. The authors present the case of a 14-year-old boy with sudden cardiac arrest due to ventricular fibrillation and myocardial infarction as a result of butane gas inhalation. Coronary angiography revealed normal coronary arteries. Cardioverter-defibrillator was implanted as a secondary prophylaxis of sudden cardiac death.