Accurate Quantum Chemical Prediction of Gas-Phase Anion Binding Affinities and Their Structure-Binding Relationships.

This paper systematically examines the performance of contemporary wavefunction and density functional theory methods to identify robust and cost-efficient methods for predicting gas-phase anion binding energies. This includes the local coupled cluster LNO-CCSD(T) and DLPNO-CCSD(T), as well as double-hybrid DSD-PBEP86-D3(BJ) and various hybrid functionals M06-2X, B3LYP-D3(BJ), ωB97M-V, and ωB97X-V. The focus is on dual-hydrogen-bonding anion receptors that are commonly found in supramolecular chemistry and organocatalysis, namely, (thio)ureas, deltamides, (thio)squaramides, and croconamides as well as the yet-to-be-explored rhodizonamides. Of the methods examined, M06-2X emerged as the overall best performing method as the other functionals including DSD-PBEP86-D3(BJ) and the local coupled cluster DLPNO-CCSD(T) method displayed systematic errors that increase with the degree of carbonylation of the receptors. Hybrid ONIOM models that employed semiempirical methods (PM7, GFN1-xTB, and GFN2-xTB) and "threefold"-corrected small-basis set potentials (HF-3c, B97-3c, and PBEh-3c) were explored, and the best models resulted in 50- to 500-fold reduction in CPU time compared to W1-local. These calculations provide important insight into the structure-binding relationships where there is a direct correlation between Brønsted acidity and anion binding affinity, though the strength of the correlation also depends on other factors such as hydrogen-bonding geometry and the geometrical distortion that the receptor needs to undergo to bind the anion.

Accuracy of DLPNO-CCSD(T): Effect of Basis Set and System Size.

The DLPNO-CCSD(T) method is designed to study large molecular systems at significantly reduced cost relative to its canonical counterpart. However, the error in this approach is also size-extensive and relies on cancellation of errors for the calculation of relative energies. This work provides a direct comparison of canonical CCSD(T) and TightPNO DLPNO-CCSD(T) calculations of reaction energies and barriers of a broad range of chemical reactions. The dataset includes acidities, anion binding affinities, enolization, Diels-Alder, nucleophilic substitution, and atom transfer reactions and complements existing theoretical datasets in terms of system size as well as new reaction types (e.g., anion binding affinities and chlorine atom transfer reactions). The performance of DLPNO-CCSD(T) was further examined with respect to systematic variation of basis set and system size and amounts of nonbonded interaction present in the system. The errors in the DLPNO-CCSD(T) were found to be relatively insensitive to the choice of basis set for small systems but increase monotonically with system size. Additionally, calculations of barriers appear to be more challenging than reaction energies with errors exceeding 5 kJ mol-1 for many Diels-Alder reactions. Further tests on three realistic organic reactions reveal the impact of the DLPNO approximation in calculating absolute and relative barriers that are important for predictions such as stereoselectivity.

Primary neuroectodermal tumor of penis (PNET)--a case report.

Primary neuroectodermal tumor (PNET) is a rare entity with high malignant potential. It usually affects the skeletal system and primary extraskeletal involvement is uncommon. Because of rarity of tumor in the penis, only a few cases have been reported. A 17-year-old male adolescent presented with painless penile swelling of 4 weeks' duration. Clinical examination revealed multiple, 1 cm hard nodules palpable on penile shaft. Open incisional biopsy of the penile nodule revealed an undifferentiated malignant round cell tumor and on immunohistochemistry a diagnosis of PNET was made. Metastatic workup was negative. Total penectomy and perineal urethrostomy was performed, and subsequently adjuvant chemotherapy was given.

Pheochromocytoma of urinary bladder - a case report.

Pheochromocytomas are catecholamine producing neuroendocrine tumours. Bladder involvement with pheochromocytoma is rare that usually presents with hypertension, hematuria and syncope often related to voiding. Clinical manifestation may be inconsistent and high index of suspicion is required for accurate diagnosis. We report a case, who presented with gross intermittent hematuria and mild elevation of pulserate and bloodpressure. Patient was adequately treated with partial cystectomy.