Theoretical Spectroscopic Study of Normal Raman and Charge Transfer Surface-Enhanced Raman Scattering (SERS) Spectra of the Adsorbed l- and d-Cysteine on the Chiral Au34 and Ag4@Au30 Nanoclusters: Chirality Discrimination.

In this work, the discrimination of the enantiomers of cysteine (l- and d-CYS) using the chiral Au34 and Ag4@Au30 clusters was theoretically investigated in the gas phase and water. Two modes were considered for the interaction of each enantiomer with the clusters (via only its S atom or its S atom and NH2 group, simultaneously). The interaction energy (Eint) and adsorption energy (Ead) for the complexation of each enantiomer with the clusters for each interaction mode were calculated. Considering the calculated interaction energies, the interaction of d-CYS with Au34 is stronger than that of l-CYS with the same cluster. Also, it was observed that the substitution of the Au4 core of the Au34 cluster with the Ag4 cluster caused the increase of the interaction energy of l-CYS with the Ag4@Au30 cluster compared to the Au34 cluster, while the reverse trend was observed for d-CYS. Quantum theory of atoms in molecules (QTAIM) analysis was employed to calculate the interaction paths and their related bond critical points (BCPs) between the CYS enantiomers and the clusters to explain the difference between the interaction energy of the enantiomers with the clusters. The IR, normal Raman (NR), and surface-enhanced Raman scattering (SERS) spectra of the enantiomers interacting with the Au34 and Ag4@Au30 clusters were calculated, and the discrimination between l-CYS and d-CYS using the calculated spectra was explained. It was found that the discrimination of the enantiomers based on their interaction with the clusters is controlled by the charge transfer between the enantiomers and the clusters.

A curcumin-nicotinoyl derivative and its transition metal complexes: synthesis, characterization, and in silico and in vitro biological behaviors.

Curcumin-nicotinoyl (Cur-Nic) was synthesized by the chemical modification of the curcumin structure, characterized, and used as a ligand for the synthesis of copper(II) and zinc(II) complexes. The biological activities of Cur-Nic and its metal complexes were predicted using the PASS and Swiss Target Prediction online software, respectively, and docking studies with tyrosine-protein kinase SRC were performed using the PyRx software to predict their anticancer activities. The toxicity effects of the complexes on a human breast cancer cell line (MCF-7) compared to a healthy breast cell line (MCF-10A) were investigated by the MTS assay. Although the metal complexes maintained the least toxicity against normal cells, the results indicated that compared to curcumin and Cur-Nic, the cytotoxicity toward cancer cells increased due to the complexation process. Moreover, the antibacterial evaluation of the compounds against a Gram-positive bacterium (MRSA) and a Gram-negative bacterium (E. coli) indicated that the Cu(II) complex and Cur-Nic were the best, respectively. Also, the Zn(II) complex was the most stable compound, and the Cu(II) complex was the best ROS scavenger based on the in vitro evaluation.

Orbital histiocytosis and fibrohistiocytosis: the clinicopathological characteristics of 117 patients, over a decade of experience.

PURPOSE: To describe the clinicopathological features of a large cohort of patients with orbital histiocytoses and fibrohistiocytosis, such as Langerhans cell histiocytosis (LCH) and non-LCH disorders, and correlate patients' clinical characteristics with their pathological diagnosis. METHODS: In this retrospective study, medical records of patients presenting to Farabi Eye Hospital, a tertiary eye care center in Tehran, Iran, from 2010 until 2022, were reviewed. Patients' demographics, chief complaint, location and laterality of the tumor, best-corrected visual acuity, presence of bone erosion on imaging, and their pathological diagnosis were retrieved. Excisional biopsy was performed and evaluated through light microscopy and immunohistochemistry study for their respective markers, including CD1a, CD68, CD207, and S100. RESULTS: A total of 117 patients with 11 pathological subtypes of histiocytoses and fibrohistiocyosis were identified, with 56.4% male and 43.6% female patients. The mean age at presentation was 23.4 years (range 1.5 months-73 years). Swelling and palpable mass were the most common chief complaints. LCH was the most common pathology (32.5%), followed by juvenile xanthogranuloma (26.5%) and adult xanthogranuloma (21.4%). Age, lesion location, and bone erosion had a statistically significant difference among the various diagnosed subtypes. CONCLUSIONS: Histiocytoses and fibrohistiocytosis are diverse and rare disorders potentially involving multiple organ systems. Ophthalmic manifestations of these diseases are even more uncommon. We reviewed their orbital presentation along with their respective histopathological findings. Our results also suggested that an orbital CT scan can be of diagnostic value to discriminate LCH from other histiocytic pathologies.

A Case Series of Infectious Keratitis After Corneal Cross-linking.

PURPOSE: To present the 7-year experience of a tertiary eye hospital while exploring possible risk factors and incidence of infectious keratitis in patients undergoing standard corneal cross-linking (CXL). METHODS: This retrospective cohort study included patients with progressive keratoconus undergoing standard CXL in the Farabi Eye Hospital and all other patients who had undergone CXL in other facilities and were diagnosed as having infectious keratitis in the 7-year period of the study. RESULTS: Among the total of 4,863 eyes that underwent CXL, 6 eyes developed infectious keratitis, yielding an incidence rate of 0.12%. Additionally, 13 eyes from 10 patients with a CXL history in other facilities who developed infectious keratitis were included. The mean age was 23.75 years, and 75% of patients were men and 25% were women. Gram-positive bacteria and Staphylococcus aureus were the most prevalent pathogens. Meibomian gland dysfunction, dry eye disease, or blepharitis were present in 12 patients. Medical treatment did not arrest the disease progress in 5 patients, which eventually required cases to undergo keratoplasty. CONCLUSIONS: This study supports the need for proper patient selection by using a comprehensive medical history. It also highlights the imperative role of rigorous patient education and follow-up, particularly in the first postoperative week. Finally, the study emphasizes aggressive early therapy for patients with suspicious findings. [J Refract Surg. 2023;39(8):564-572.].

Charge Transfer Surface-Enhanced Raman and Absorption Spectra of the Zwitterionic Form of Cysteine Adsorbed on M@Au12 (M = Au, Ag, Pt, and Pd) Nanoclusters.

The effect of the core atom type of the M@Au12 nanocluster (M = Au, Ag, Pt, and Pd) on the normal (NR) and charge-transfer surface-enhanced Raman spectroscopy (CT-SERS) of the zwitterion form of l-cysteine (ZWCYS) adsorbed on two different sites (D1 and D2) of the nanocluster is investigated separately in the gas phase and water. Because SERS requires the calculation of the absorption spectrum, the effect of the core atom type on the absorption spectrum of M@Au12 and its complex with the ZWCYS has also been investigated. The vibrational bands that show the intensity enhancement in the CT-SERS of the ZWCYS interacting with the D1 site of M@Au12 nanocluster in water are O─C═O asymmetric stretching (M = Au and Ag), NH2 bending (M = Ag), S-H stretching (M = Ag, Pt, and Pd), CH2 bending (M = Pt), and CH2 symmetric stretching (M = Pt and Pd). The ZWCYS at the D2 site of the M@Au12 nanocluster in water exhibits intensity enhancement for O─C═O asymmetric stretching (M = Pt), NH3 wagging (M = Au), and S-H stretching (M = Pd). The intensity of the vibrational bands of ZWCYS does not increase for M = Ag but decreases for O─C═O asymmetric stretching, S-H stretching, CH2 symmetric stretching, CH2 asymmetric stretching, and especially NH2 symmetric stretching.

Post photorefractive keratectomy (PRK) infectious keratitis; six-year experience of a tertiary eye hospital.

BACKGROUND/OBJECTIVES: As an essential development in the new century, surface ablation procedures have attracted increasing attention. There exists a concern regarding the risk of infectious keratitis. Hence, we aimed to investigate the rate and predisposing factors of infectious keratitis after photorefractive keratectomy (PRK). SUBJECTS/METHODS: This retrospective study was designed in two phases. First, the rate of post-PRK keratitis of Farabi Eye Hospital was investigated. In other words, the targeted population was the patients who developed keratitis after performing procedure at Farabi Eye Hospital. In the second phase, all the patients with the diagnosis of post-PRK keratitis were studied regardless of the centre where surgery was performed. Patients with the diagnosis of infectious keratitis between 2014 and 2020 were enrolled and following information was analyzed: demographics, presentation time after surgery, perioperative medications, culture results, risk factors, medical treatment, complications, and final visual acuity. RESULTS: The total number of PRK procedures in our centre was 24,986 (13,253 patients), in which 6 eyes of 5 patients developed keratitis. Beside these 5 patients, 24 referred patients (24 eyes) from the other centres were enrolled. Finally, a total number of 29 patients (30 eyes) were included. Our analysis revealed that manipulation of contact lens, dry eye, and blepharitis were the essential predisposing factors for keratitis development. CONCLUSION: The overall post-PRK keratitis occurrence rate of our study was 0.02%. Our observation highlighted the importance of preoperative examination and treatment of the lids and dry eye disease.

Circular RNA MYLK as a prognostic biomarker in patients with cancers: A systematic review and meta-analysis.

BACKGROUND: Circular RNA (circRNA) myosin light chain kinase (circMYLK) has recently received increasing attention in cancer biology. Several studies have suggested that circMYLK expression is linked to prognosis and clinicopathological characteristics of various malignancies. AIMS: This study was carried out to systematically review the impact of circMYLK on the progression of multiple cancers and assess the significance of circMYLK in the prognosis and clinicopathological features of the patients. METHODS: PubMed, Web of Science, and Embase were systematically searched until July 2, 2021. For qualitative synthesis, the signaling pathways of circMYLK in the progression of different cancers were summarized. Regarding the meta-analysis, overall survival (OS) and eight clinicopathological characteristics of patients with cancers were addressed. Odds ratios (ORs) and hazard ratios (HRs) were calculated to assess the association of circMYLK with prognostic and clinicopathological features. RESULTS: Twelve studies investigating the role of circMYLK in cancer progression met the inclusion criteria. Among these, seven studies investigated the prognostic significance of circMYLK, and nine studies ascertained the clinicopathological importance of circMYLK in patients with various malignancies. CircMYLK acts as a tumor promoter circRNA, leading to migration, proliferation, invasion, and metastasis of neoplastic cells and inhibiting their apoptosis through interaction with several miRNAs and corresponding downstream signaling pathways. Overexpression of circMYLK was correlated with poor OS (HR = 1.75; 95% confidence interval [CI] 1.52-2.02) and larger tumor size (OR = 2.90; 95% CI 1.03-8.15), higher T stage (OR = 2.49; 95% CI 1.20-5.18), lymph node metastasis (OR = 2.55; 95% CI 1.41-4.62), and higher TNM stage (OR = 4.62; 95% CI 2.99-7.14). CONCLUSIONS: CircMYLK is involved in the progression of numerous cancers via different signaling pathways. This circRNA can serve as a promising prognostic biomarker for several types of malignancies. Furthermore, high expression of circMYLK is associated with advanced clinicopathological characteristics in various tumors.

Oncologic outcomes of Bacillus Calmette-Guérin therapy in elderly patients with non-muscle-invasive bladder cancer: A meta-analysis.

INTRODUCTION: There is a challenge on the medical efficacy of intravesical Bacillus Calmette-Guérin (BCG) therapy and the power of the immune system boosting, which can be influenced by the age of the non-muscle-invasive bladder cancer (NMIBC) patients. This meta-analysis evaluates the efficacy of BCG therapy among aged (>70) and younger patients with non-muscle-invasive bladder cancer (NMIBC). METHODS: The central database of PubMed, Scopus, and Web of Science were queried until August 4, 2021, by using "BCG," "Bladder Cancer," "AGE," and "efficacy" keywords. After excluding duplicated results, titles and abstracts were evaluated by two independent reviewers. The exclusion criteria included non-English studies, conference abstracts, reviews, editorials, letters, and comments. Three main outcomes, disease-free survival (DFS), progression-free survival (PFS), and cancer-specific survival (CSS), were considered. The statistical analysis was performed using STATA (version 14; Stata Corp, College Station, Texas, USA). RESULTS: From 1115 found documents, the 24 research articles were recruited in the systematic review, and 10 were the candidate for meta-analysis. The overall estimate of H.R. revealed that BCG therapy in those over age 70 is significantly associated with an improved risk of progression and cancer-specific death in studied patients. However, this association was not statistically significant for DFS (1.04 (95% CI: 0.85,1.26)). CONCLUSION: The BCG maintenance therapy improved CSS and PFS oncological outcomes in elderly patients with NMIBC. BCG therapy did not significantly change the DSF.

Increased Rate of Infectious Keratitis After PRK in the COVID-19 Era: The Possible Role of Face Masks.

PURPOSE: To evaluate the rate of infectious keratitis after photorefractive keratectomy (PRK) before and during the coronavirus disease 2019 (COVID-19) pandemic. METHODS: A retrospective chart review was performed on patients who were diagnosed as having infectious keratitis after PRK between January 2015 and January 2021. RESULTS: The study period was divided into the pre-COVID-19 era (between January 2015 and February 2020) and the COVID-19 era (between February 2020 and January 2021). A total of 47 patients were diagnosed as having infectious keratitis after PRK: 22 were diagnosed in the pre-COVID-19 era and 25 were diagnosed in the COVID-19 era. The rate ratio for infectious keratitis after PRK was 5.68 during the COVID-19 pandemic (CI: 3.20 to 10.07, P < .001). The odds ratio for the ratio of cases of infectious keratitis after PRK to all cases of infectious keratitis was 9.00 during the COVID-19 pandemic (CI: 5.05 to 16.05, P < .001). To better understand the change in the rate of infectious keratitis after PRK during the COVID-19 pandemic, the analysis was narrowed to the patients with infectious keratitis who had their procedure in Farabi Eye Hospital. Of the 8 patients who were diagnosed as having infectious keratitis after PRK, 4 were diagnosed in the pre-COVID-19 era and 4 were diagnosed in the COVID-19 era. The risk ratio of infectious keratitis after PRK was 9.11 in our department in the COVID-19 era (95% CI limit: 2.28 to 36.46, P = .005). CONCLUSIONS: The rate of infectious keratitis after PRK increased during the COVID-19 pandemic. This may be due to the increased use of face masks in this era. [J Refract Surg. 2022;38(2):78-81.].

Long non-coding RNAs (lncRNAs) as prognostic and diagnostic biomarkers in multiple myeloma: A systematic review and meta-analysis.

BACKGROUND: Recently, emerging studies have demonstrated the utility of particular long non-coding RNAs (lncRNAs) as useful biomarkers for the diagnosis and prognosis of multiple myeloma (MM). We systematically reviewed the literature and conducted a meta-analysis to quantify the predictive effectiveness of lncRNAs in the prognosis and diagnosis of MM. METHODS: A systematic search was performed in PubMed, Embase, and Web of Science until March 24, 2021. A meta-analysis was conducted to explore the correlation between the expression of lncRNAs and prognostic endpoints, including overall survival (OS), progression-free survival (PFS), and disease-free survival (DFS) or event-free survival (EFS). Moreover, the diagnostic performance of lncRNAs in MM was investigated by calculating accuracy metrics. RESULTS: Overall, 43 studies were included in this systematic review, amongst which 36 studies assessed prognostic endpoints (including 5499 participants and 69 lncRNAs), and 11 studies evaluated diagnostic outcomes (with 1723 participants and 11 lncRNAs). The overexpression of CRNDE (hazard ratio (HR)= 1.94, 95% confidence interval (CI) 1.61, 2.34), NEAT1 (HR=1.97, 95%CI 1.36, 2.85), PVT1 (HR=1.92, 95%CI 1.25, 2.97), and TCF7 (HR=1.98, 95%CI 1.42, 2.76) was significantly associated with reduced OS. Furthermore, upregulation of PVT1 was significantly correlated with poor PFS (HR=1.86, 95%CI 1.29, 2.68). The pooled diagnostic performance of lncRNAs was as follows: sensitivity 0.78 (95%CI 0.73, 0.82), specificity 0.88 (95%CI 0.83, 0.92), and area under the curve 0.89 (95%CI 0.86, 0.92). CONCLUSIONS: Our results revealed the potential significance of lncRNAs in MM as diagnostic and prognostic markers, which may be the future targets for individualized therapy.

Squamous cell carcinoma of the lung and pulmonary metastasis of papillary thyroid carcinoma: a case report.

BACKGROUND: The coexistence of malignancies in a patient may be explained by the tumor-to-tumor metastasis phenomenon or multiple primary malignant tumors, both of which are not common findings. Here, we are going to present a case with coexistent papillary thyroid carcinoma and primary squamous cell carcinoma of the lung. CASE PRESENTATION: A 36-year-old Iranian man presented to our clinic for evaluation of constitutional symptoms. His past medical history was significant for papillary thyroid carcinoma due to which he had undergone total thyroidectomy, cervical lymph node dissection, and radioactive iodine therapy 14 years ago. Six months prior to admission, he received radioactive iodine therapy due to the metastatic involvement of both lungs with papillary thyroid carcinoma in another center with consequent improvement in symptoms. Diffuse nodular lesions in both lungs, a lesion in the lower lobe of his left lung, not present 6 months ago, peritoneal carcinomatosis, and several para-aortic lymphadenopathies were detected by imaging studies. A radioactive iodine uptake scan, positron emission tomography/computed tomography scan, and transbronchial biopsy of the lesion in the lung revealed concurrent squamous cell carcinoma of the lung and pulmonary metastasis of papillary thyroid carcinoma. After consultation with an oncologist, our patient received 6 months of chemotherapy; however, he died 8 months after presentation. CONCLUSIONS: Physicians should be aware of the possibility of the emergence of primary malignancies in patients with a history of papillary thyroid carcinoma, especially lung cancer as it is a common site of papillary thyroid carcinoma metastases. Using appropriate diagnostic evaluations in order to choose the best therapeutic option is of utmost importance.

Immobilization of gold nanoparticles on folate-conjugated dendritic mesoporous silica-coated reduced graphene oxide nanosheets: a new nanoplatform for curcumin pH-controlled and targeted delivery.

In the present study, a new sandwich-like nanocomposite as a multifunctional smart nanocarrier for curcumin (Cur) targeted delivery and cell imaging was prepared by immobilization of gold nanoparticles on folic acid-modified dendritic mesoporous silica-coated reduced graphene oxide nanosheets (AuNPs@GFMS). The physical and chemical properties of the nanocomposite were investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis, field-emission scanning electron microscopy (FE-SEM), Fourier transformation infrared (FT-IR), and Brunauer-Emmett-Teller (BET) surface area analysis. The nanocarrier exhibits a number of interesting properties, including good biocompatibility, biodegradability, and suitable surface area, which results in high drug loading capacity. In addition, this new drug delivery system showed sustained-release and pH-responsive properties. The in vitro cytotoxicity test of the free curcumin, free nanocarrier (AuNPs@GFMS), curcumin-loaded folate-conjugated nanocarriers (Cur-AuNPs@GFMS), and curcumin-loaded nanocarriers without folate-conjugation (Cur-AuNPs@GAMS) against two human cancer cell lines, including MCF-7 (human breast carcinoma cell lines) and A549 (human lung carcinoma cell lines) demonstrated that the therapeutic efficacy of Cur-AuNPs@GFMS is significantly greater than those of other compounds because the cancerous cells can uptake the folate-conjugated drug nanocarrier via a receptor-mediated mechanism. Fluorescence microscopic images and different staining techniques were also used to visualize the cellular uptake, anticancer activity, specific targeting ability, and photothermal potency of Cur-AuNPs@GFMS toward the MCF-7 cancer cells. The obtained results proved that the proposed system, Cur-AuNPs@GFMS, can be used as a potent anticancer agent in targeted cancer therapies for breast cancer.

Synthesis and spectroscopic characterization study of new palladium complexes containing bioactive O,O-chelated ligands: evaluation of the DNA/protein BSA interaction, in vitro antitumoural activity and molecular docking.

[Pd{(C,N)-C6H4CH2NH(Et) (Qu)] (2) and [Pd{(C,N)-C6H4CH2NH(Et) (Nar)] (3) (Qu = Quercetin, Nar = Naringin) mononuclear palladium (II) complexes have been synthesized and characterized using elemental analysis, IR and electronic spectroscopy. The interaction of the prepared complexes with calf thymus DNA and bovine serum albumin (BSA), monitored by UV-visible and fluorescence titrations, respectively, have been carried out to better understand the mode of their action under biological conditions. Intercalative binding mode between the complexes and DNA is suggested by the binding constant (Kb) values of 2.5 × 106 and 3.2 × 106 for complexes 2 and 3, respectively. In particular, the in vitro cytotoxicity of the complexes on two cancer cells lines (bladder carcinoma TCC and breast cancer MCF7) showed that the compounds had broad spectrum, anti-cancer activity with low IC50 values and the order of in vitro anticancer activities is consistent with the DNA-binding affinities. In the meantime, the quenching of tryptophan emission with the addition of complexes using BSA as a model protein indicated the protein binding ability. The quenching mechanisms of BSA by the complexes were static processes, according to the results obtained. The competitive binding using Warfarin, Digoxin and Ibuprofen site markers, which contain definite biding sites, demonstrated that the complexes bind to site I on BSA. Ultimately, the binding sites of DNA and BSA with the complexes have been determined by molecular modelling studies.

Quantum mechanical/molecular mechanical and docking study of the novel analogues based on hybridization of common pharmacophores as potential anti-breast cancer agents.

In an attempt to identify some new potential leads as anti-breast cancer agents, novel hybrid compounds were designed by molecular hybridization approach. These derivatives were structurally derived from hybrid benzofuran-imidazole and quinazolinone derivatives, which had shown good cytotoxicity against the breast cancer cell line (MCF-7). Since aromatase enzyme (CYP19) is highly expressed in the MCF-7 cell line, the binding of these novel hybrid compounds to aromatase was investigated using the docking method. In this study, due to the positive charge on the imidazole ring of the designed ligands and also, the presence of heme iron in the active site of the enzyme, it was decided to optimize the ligand inside the protein to obtain more realistic atomic charges for it. Quantum mechanical/molecular mechanical (QM/MM) method was used to obtain more accurate atomic charges of ligand for docking calculations by considering the polarization effects of CYP19 on ligands. It was observed that the refitted charge improved the binding energy of the docked compounds. Also, the results showed that these novel hybrid compounds were adopted properly within the aromatase binding site, thereby suggesting that they could be potential inhibitors of aromatase. The main binding modes in these complexes were through hydrophobic and H bond interactions showing agreement with the basic physicochemical features of known anti aromatase compounds. Finally, the complex structures obtained from the docking study were used for single point QM/MM calculations to obtain more accurate electronic interaction energy, considering the electronic polarization of the ligand by its protein environment.

Synthesis, structure, DNA/protein binding, and cytotoxic activity of a rhodium(III) complex with 2,6-bis(2-benzimidazolyl)pyridine.

A new mononuclear rhodium(III) complex, [Rh(bzimpy)Cl3] (bzimpy = 2,6-bis(2-benzimidazolyl)pyridine), was synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structure of the complex was confirmed by single-crystal X-ray crystallography. The interaction of the complex with fish sperm DNA (FS-DNA) was investigated by UV spectroscopy, emission titration, and viscosity measurement in order to evaluate the possible DNA-binding mode and to calculate the corresponding DNA-binding constant. The results reveal that the Rh(III) complex interacts with DNA through groove binding mode with a binding affinity on the order of 104. In addition, the binding of the Rh(III) complex to bovine serum albumin (BSA) was monitored by UV-Vis and fluorescence emission spectroscopy at different temperatures. The mechanism of the complex interaction was found to be static quenching. The thermodynamic parameters (ΔH, ΔS, and ΔG) obtained from the fluorescence spectroscopy data show that van der Waals interactions and hydrogen bonds play a major role in the binding of the Rh(III) complex to BSA. For the comparison of the DNA- and BSA-binding affinities of the free bzimpy ligand with its Rh(III) complex, the absorbance titration and fluorescence quenching experiments of the free bzimpy ligand with DNA and BSA were carried out. Competitive experiments using eosin Y and ibuprofen as site markers indicated that the complex was mainly located in the hydrophobic cavity of site I of the protein. These experimental results were confirmed by the results of molecular docking. Finally, the in vitro cytotoxicity properties of the Rh(III) complex against the MCF-7, K562, and HT-29 cell lines were evaluated and compared with those of the free ligand (bzimpy). It was found that the complexation process improved the anticancer activity significantly.

Ionization of vitamin C in gas phase: Theoretical study.

In this work, the gas phase ionization energies and photoelectron spectra of four important conformers of vitamin C were calculated. Symmetry adapted cluster/configuration interaction methodology employing the single and double excitation operators (SAC-CI SD-R) along with D95++(d,p) basis set were used for the calculations. Thermochemistry calculations were also performed on all possible conformers of vitamin C to find the relative stability of conformers in the gas phase. The calculated ionization bands of each conformer were assigned by calculating the contribution of natural bonding orbital (NBO) in the calculated canonical molecular orbitals involved in the ionization. SAC-CI calculations showed that the first ionization band of vitamin C is related to the π electrons of CC bond of the ring of molecule although, there is the lone electron pairs of oxygen atoms and π electrons of CO bond in the molecule.

Experimental and theoretical spectroscopic study and structural determination of nickel(II) tridentate Schiff base complexes.

Some new complexes of [NiL(PR3)] (where L=(E)-1-[(2-amino-5-nitrophenyl)iminio-methyl]naphthalene-2-olate (L(1)), (E)-1-[(2-hydroxiphenyl)iminio-methyl]naphthalene-2-olate (L(2)), R=Bu and Ph) containing tridentate ONN and ONO Schiff bases were synthesized and characterized by IR, UV-Vis, (1)H-NMR spectroscopy and elemental analysis. The geometry of [NiL(1)(PBu3)] and [NiL(2)(PBu3)] complexes were determined by X-ray crystallography. It was indicated that the complexes have a square planar structure and four coordinates in the solid state. Theoretical calculations were also performed to optimize the structures of the ligands and complexes in the gas phase and ethanol solvent, separately to confirm the structures proposed by X-ray crystallography. In addition, UV-Visible and IR spectra of the complexes were calculated and compared with the corresponding experimental spectra to complete the experimental structural identification.

DFT and MP2 study of low barrier proton transfer in hydrazide schiff base tautomers via water bridges and in the gas.

MP2 and DFT studies were performed on the tautomers of N'-ethylideneacetohydrazide in different environments including gas phase, continuum solvent and microhydrated environment. The ground electronic state structures of the tautomers were optimized at the MP2 and B3LYP levels of theory using 6-311++G(d,p), separately. The optimized geometries of the transition states of different tautomerism processes, which occur through the proton transfer (PT) reaction, were determined using the QST3 approach at the same levels of theory. The same stability order as T1Z[Symbol in text] T2ZE[Symbol: see text] T2ZZ[Symbol in text] T2EE[Symbol in text] T2EZ[Symbol in text] T6[Symbol in text] T4E was found for the tautomers in the gas phase, continuum solvent and microhydrated environment for both B3LYP and MP2 levels of theory. In addition, the variations of the Gibbs free energies of tautomeric processes, the activation Gibbs free energies of the forward and reverse tautomeric processes with the polarity of the solvent (in continuum solvent model) and the number of water molecules (in microhydrated environment) were investigated. It was found that the reverse tautomeric process is more favorable in all considered environments thermodynamically and kinetically. In addition, it was shown that the rate constants of the reverse and forward considered tautomeric processes decrease with the solvent polarity in the continuum solvent model and the process becomes more difficult than the gas phase. The opposite trend is seen in the microhydrated environment.