Patterns of failure in patients with nasopharyngeal cancer of Northeastern region of India: a retrospective observational study.

PURPOSE: We aimed to analyze patterns of failure and disease volume-treatment outcomes in patients with Nasopharyngeal carcinoma (NPC) treated with definitive radiation with or without concurrent chemotherapy at a tertiary cancer centre in northeast India. METHODS: From February 2018 to February 2022, 99 histopathologically proved non-metastatic NPC patients treated with curative-intent RT with or without chemotherapy were retrospectively analyzed. Locally advanced patients received neoadjuvant or adjuvant chemotherapy. The Cox proportional hazards model was used to investigate the impact of various prognostic factors on locoregional free survival (LRFS), distant metastasis free survival (DMFS), progression free survival (PFS) and overall survival (OS). The log-rank test and Kaplan-Meir curves compared outcome variables based on ROC analysis-classified tumor volume. RESULTS: During a median follow up of 25.4 months (17.3-39.2), 35(35.4%) patients developed recurrence. Twenty-three patients developed locoregional failures, of which 11 were in-field; 12 patient showed an out-field failure. The 3-year LRFS, DMFS, PFS and OS was 71.10%, 70.90%, 64.10% and 74.10% respectively. There was statistically significant difference in LRFS according to T staging (p < 0.0001). Gross tumor volume (GTVp) and gross nodal volume (GTVn) were an independent prognostic factor for OS, PFS, LRFS and DMFS. The cut-off volumes for GTVp and GTVn for distant metastases and locoregional failure, respectively, were found to be 13 and 22.7 mL and 3.7 and 39.2 mL, respectively, by ROC curve analysis. Based on this, 99 patients were divided into three subgroups. OS demonstrated significant differences among patients in different volume subgroups for GTVp (p = 0.03) and GTVn (p = 0.00024). CONCLUSIONS: For NPC patients who undergo curative IMRT, primary tumour and nodal volumes are independent prognostic indicators. GTVp and GTVn are highly predictive of local control, distant metastases, disease-free survival, and overall survival. This justifies their use as quantitative prognostic indicator for NPC.

Stereotactic Body Radiation Therapy in Recurrent Head and Neck Cancer: Where Do We Stand?

This review explores the difficulties encountered in the management of head and neck cancer (HNC), with special attention to the challenges presented by locoregional recurrences, which impact a substantial number of patients. While maximal surgical resection remains the gold standard for treatment, surgery is often not feasible due to various factors. In such cases, reirradiation has emerged as a potential strategy, albeit with a heightened risk of severe toxicity. Stereotactic Body Radiation Therapy (SBRT) is introduced as a promising approach for unresectable recurrent HNC. SBRT offers precise radiation doses and shorter treatment durations, making it a potentially optimal treatment modality. Despite the growing interest in SBRT, there is a lack of consensus guidelines for its use in HNC, particularly in India. Nevertheless, recommendations are provided for the benefit of SBRT in reirradiation settings, considering factors like tumour size, dose, and treatment duration. The article highlights the safety and effectiveness of SBRT-based reirradiation with existing evidence. The literature review discusses various studies and their findings, emphasizing the importance of high-dose SBRT for improved overall survival. The article also explores the combination of SBRT with systemic therapy as a potential synergistic approach to enhance patient outcomes. In conclusion, SBRT shows promise as a valuable therapeutic tool for patients with inoperable recurrent HNC, offering acceptable safety. However, further research and well-designed trials are needed to optimize its use and identify the most suitable patient cohorts. Establishing comprehensive working guidelines and a nationwide prospective database will be crucial in advancing this treatment approach.

Evaluation of Cardiac Substructures Dose Sparing in Single and Dual Isocenter RapidArc™ Radiotherapy Planning for Synchronous Bilateral Breast Cancer.

Purpose This study compares the dosimetry and dose sparing of cardiac substructures in single isocenter and dual isocenter RapidArc™ (Varian Medical Systems, Palo Alto, California, United States) radiotherapy planning for synchronous bilateral breast cancer. Methodology Six synchronous bilateral breast cancer (SBBC) patients received adjuvant radiation with the prescribed dose of 40.05 Gy in 15 fractions to the planning target volume (PTV) without local lymph nodal regions. PTVs and organs at risk (OARs), including both lungs, esophagus, spinal cord, heart, and left anterior descending coronary artery (LAD), both atria and ventricles were contoured. Single isocentric RapidArc (SIRA) and dual isocentric RapidArc (DIRA) plans were made for each patient and dosimetric differences between these two techniques were evaluated. Results There was no statistically significant difference in conformity index (CI) values between SIRA and DIRA plans, with 0.9681±0.01 and 0.9721±0.01 (p=0.505), respectively. SIRA planning showed superior homogeneity with homogeneity Index (HI) values of 0.0999±0.01 compared to DIRA planning with HI values of 0.1640±0.12 (p=0.230). The mean LAD dose of SIRA was valued higher than that of DIRA planning. Lower mean doses were obtained for both lungs in SIRA plans compared to DIRA plans. Meanwhile, doses to the right atrium, left atrium, left ventricle, right ventricle, and esophagus showed no statistical significance between these two techniques, except in the spinal cord. Conclusion Both SIRA and DIRA plans have satisfactory outcomes in sparing OARs. Meanwhile, SIRA techniques have less setup time and overall machine time.

Definitive Radiotherapy in Locally Advanced Head and Neck Squamous Cell Cancer with Clinical Extranodal Extension.

Purpose: The extranodal extension (ENE) in head and neck squamous cell carcinoma (HNSCC) is a potential poor prognostic factor. Clinical ENE (cENE) was incorporated in the HNSCC staging system in the 8th edition of AJCC. There is not much evidence to support the treatment of HNSCC with cN3b with radiotherapy in radical intent. This study aims to assess the treatment outcome in patients of HNSCC with cN3b disease treated with definitive radiotherapy. Method: Forty-five HNSCC patients with cN3b disease treated with definitive radiotherapy with or without concurrent chemotherapy between January 2018 to December 2018 were retrospectively evaluated. Results: The median age of the study patients was 60 years (40-75years). Only 35 patients (77.8%) could complete the prescribed course of treatment, and the leading common cause of non-completion was treatment-related toxicities. After a median follow-up period of 9.3 months (range 2-33), the median OS and PFS were 22.6 months and 7.2 months, respectively. Fourteen patients (31.1%) in our study developed grade III/IV mucositis, and 11 (24.4%) developed severe grade III/IV dermatitis. The locoregional failure constituted 24 patients (53.3%). Conclusion: The treatment outcome of HNSCC with cN3b disease is inferior. A personalized and subjective approach should be undertaken before choosing radiotherapy with a radical intent in this group of patients.

Prognostic Significance of Neutrophil-Lymphocyte Ratio in Patients of High-Grade Glioma Undergoing Adjuvant Chemoradiation: A Prospective Study.

PURPOSE: High-grade gliomas are highly fatal disease with poor prognosis despite multimodality management. Inflammatory biomarkers are widely used for prognostication in various solid malignancies to stratify high risk patients. The current research was conducted to investigate whether any change in neutrophil-lymphocyte ratio (NLR) during adjuvant chemoradiotherapy has any prognostic significance in high-grade glioma patients. MATERIALS AND METHODS: Seventy-three biopsy proven high-grade glioma patients treated with adjuvant chemoradiotherapy were enrolled in this study. Haematological parameters were collected before treatment, weekly during treatment, and at 4th week after chemoradiotherapy along with baseline characteristics. Overall survival (OS) was determined using Kaplan-Meier curve. Variables found statistically significant in univariate analysis by Cox regression model were subjected to final multivariable analysis. RESULTS: The median follow-up was around 17 months with a median OS of 17.2 months (95%CI 14.7-23). The best prognosis was seen in patients who had a baseline NLR< 3.5 with decline in NLR during treatment achieving a 1-year survival of 100% and median overall survival of 36.5 months. Patients who had baseline NLR ≥3.5 without a decline in NLR had worst prognosis with a 1-year survival of 25% (95%CI 9.4%-66.6%) and median OS of 7.1 months. On multivariate analysis, age [HR 1.025, p=0.040)], ECOG performance status≤1 [HR 0.089, p<0.001], extent of surgery [HR 0.305, p=0.001] and decline in NLR during treatment [HR 0.452, p=0.026] were found to be significant predictors of OS. CONCLUSION: This study demonstrated that NLR is a cost-effective biomarker that has prognostic significance in predicting overall survival for high-grade glioma patients.

Intensity Modulated Radiotherapy in Head and Neck Cancer: Initial Experience of the First Treated Cases from North-East India.

Head and neck cancer incidence is relatively higher in north-eastern states than in other parts of India. Intensity-modulated radiotherapy (IMRT) was first introduced in our institute in 2012 to cater the entire north-east. This study attempts to assess the treatment outcomes and prognostic factors of head and neck cancer patients who had been treated with definitive radiotherapy in our institute from 2012 to 2016 using IMRT. This is a single institutional retrospective study. Thirty-six patients of head and neck cancer other than nasopharynx primary treated with definitive radiotherapy using IMRT between 2012 to 2016 were evaluated. The survival was analyzed using the Kaplan-Meir method, and various clinicopathologic factors were compared. The median age of the study patients was 58 years (range 24-79 years). The majority of the patients (69.4%) were below the age of 50 years. Thirty-two patients (88.9%) were male, and only four (11.1%) were females. After a median follow-up time of 40 months (7-84 months), the 5-year overall survival (OS) was 42.1%. The stage at presentation and radiotherapy treatment time were found to be significant prognostic factors of the outcome. The treatment-related toxicities were within acceptable limits. This retrospective study has reported the outcome and treatment-related toxicities of initially treated HNC patients with IMRT from northeast India.

Factors Associated With Neurocognitive Impairment Following Chemoradiotherapy in Patients With High-Grade Glioma: Results of a Prospective Trial.

BACKGROUND: High-grade gliomas (HGG) are highly fatal tumors despite advanced multimodality management. They are also associated with neurocognitive impairment, both due to disease pathology and treatment. We aimed to assess various risk factors responsible for neurocognitive decline in HGG patients undergoing adjuvant chemoradiation. METHODS: Newly diagnosed HGG patients who underwent maximal safe resection were included. Patients received volumetric modulated arc therapy to a dose of 60 Gy in 30 fractions, along with concurrent temozolomide (TMZ) at a dose of 75 mg/m²/day orally; thereafter adjuvant TMZ (150-200 mg/m² for 5 days), given every 28 days for 6 to 8 cycles. The Mini-Mental State Examination questionnaire was used to measure cognitive impairment of each study patient at various time points. Cox regression model was used for univariate and multivariable analysis of data to establish possible risk factors. RESULTS: Fifty-three patients were enrolled and analyzed. At a median follow-up of 15 months, 30 patients (56.6%) developed cognitive impairment, and 23 patients (43.4%) did not. On univariate analysis, HGG with WHO grade 4, glioblastoma and diffuse midline glioma histology, IDH-wild type, recursive partitioning analysis class IV/V, and only biopsy of primary tumor were significantly associated with neurocognitive impairment, but none of them were independent risk factors on multivariable analysis. Planning target volume and dose received by ipsilateral hippocampus were also significantly correlated with cognitive decline in HGG patients. CONCLUSION: Decline in neurocognitive functions in HGG patients is multifactorial and can be attributed to an amalgam of various tumor, patient, and treatment-related factors.

Subjective Global Assessment of Nutritional Status in Head and Neck Cancer Patients Treated with Radiotherapy - A Prospective Observational Study from North East India.

Head and neck cancer (HNC) patients undergoing curative radiotherapy (RT) are at risk of malnutrition due to disease process as well as effects of therapy. Identifying the nutritional status of these patients at the earliest, helps to introduce adequate and timely interventions that can improve compliance and outcomes of treatment. Various tools for nutritional assessment in cancer patients have been proposed. In this prospective observational study we used the Subjective Global Assessment (SGA) questionnaire in a cohort of HNC patients receiving definitive RT at a regional cancer center of North East India. Recording of data was done at baseline, at two weekly intervals during treatment, at end of radiotherapy (EORT) and at follow-up upto 6 months. We observed that despite proper nutrition counseling, our patients suffered from malnutrition throughout their course of RT, which was at its peak by EORT but gradually improved over six months of follow-up. Pain on eating and swallowing were the most debilitating symptoms which caused significant decline of nutrient intake, body fat and muscle mass among patients together with deteriorating SGA ratings. Our results will hopefully help us design better strategies for nutrition management while delivering curative (chemo)radiotherapy for HNC patients of this region- which has one of the highest incidences of HNC in the world.

Clinical Outcomes and Prognostic Factors of Locally Advanced Nasopharyngeal Cancer Treated with Intensity Modulated Radiotherapy: First Experience Report from Northeast India.

The aim is to retrospectively evaluate the clinical outcomes and prognostic factors in patients of locally advanced nasopharyngeal cancer (NPC) treated with intensity-modulated radiotherapy (IMRT). The northeastern states report relatively more NPC cases in comparison to other states of India. This study is an attempt to assess the treatment outcomes and prognostic factors of locally advanced NPC who had been treated with definitive radiotherapy with or without chemotherapy in our institute from 2012 to 2016 using IMRT. This is a single institutional retrospective study. Thirty-one consecutive patients of locally advanced NPC treated with definitive chemoradiation using the IMRT technique between 2012 to 2016 were evaluated. The survival was analyzed using Kaplan-Meir method and their relations with various clinicopathologic parameters were compared. After a median follow-up time of 36 months, the 5-year overall survival (OS) and disease-free survival (DFS) was 47.3% and 26.1% respectively. The younger patients of < 50 years had improved OS (p = 0.05). Patients of stage IVA had inferior 5-year OS (p = 0.1) and 5-years DFS (0.02) than those of stage III. The patients who received neoadjuvant chemotherapy showed improved DFS at 5 years (p = 0.09). The treatment-related toxicities were within acceptable limit. This retrospective analysis has reported outcomes of locally advanced NPC patients treated with IMRT with concurrent chemotherapy when IMRT was first introduced in our institute. This is the first of its kind from the Northeastern region of India.

Effect of corticosteroid ointment on radiation induced dermatitis in head and neck cancer patients: A prospective study.

BACKGROUND: Almost all the patients receiving curative radiotherapy for head and neck cancer develop radiation dermatitis, which many a times leads to treatment interruption and reduce patient compliance. In this study, we evaluated the effect of potent topical steroid (Betamethasone Valerate 0.1%) cream on acute radiation dermatitis in head and neck cancer patients receiving curative radiotherapy. METHODS: A total 106 patients of head and neck cancers were randomly divided into arm A (52 patients) and arm B (54 patients). The patient in study arm A were treated with topical betamethasone 0.1% twice daily during radiotherapy/chemo-radiotherapy and arm B was kept as control. The radiation reaction in both the groups was monitored weekly according to Radiation Therapy Oncology Group (RTOG) acute radiation dermatitis grading. RESULTS: Out of 106 patients, 85 (80.2%) patients completed treatment. Patient in control arm had earlier onset of grade 1 reaction (5.7% in arm A vs 16.7 % in arm B at 2nd week, P value 0.157 and 28.8% in arm A vs 50% in arm B at 3rd week, P value 0.028) and progression of radiation dermatitis. In 7th week patient in arm A had higher grade 1 reaction (17.3% in arm A vs 0% in arm B), while arm B had higher grade 2 reaction (66.7% arm B vs 55.8% in arm A). There was no difference in incidence of grade 3 and 4 reaction. No difference was observed in time taken for reaction to heal. CONCLUSION: Topical Betamethasone can delay the onset and progression of radiation dermatitis in head and neck cancer, without significant delay in wound healing.

Definitive radiotherapy in patients of synchronous esophageal and head and neck cancer-treatment outcome and toxicity.

AIM: The aim is to retrospectively evaluate the clinical outcomes and treatment related toxicities in patients of synchronous esophageal and head & neck cancer when treated with definitive radiotherapy with or without concurrent chemotherapy. BACKGROUND: Patients of esophageal cancer with a synchronous second primary in head and neck region can be treated with definitive radiotherapy but the clinical outcome has been reported to be poor. METHOD AND DESIGN: This is a single institutional retrospective study. Twenty-five patients fulfilling inclusion and exclusion criteria were evaluated. The survival was analysed using Kaplan-Meir method and their relations with various clinicopathologic parameters were compared. RESULTS: After a median follow-up time of 14 months, the 1 year and 2 year survival was 60% and 17% respectively. Significant improvement in overall survival was observed in patients with early staged esophageal cancer then locally advanced disease (P = 0.03). Patients with locally advanced head and neck cancer had poor survival than with early stage disease (P = 0.06). Those who received concurrent chemotherapy had better survival than those with radiotherapy alone. 40% patients developed grade III & IV dermatitis and 48% patients developed grade III oral mucositis. CONCLUSION: Chemoradiotherapy can safely be offered to patients with synchronous esophageal and head and neck cancer.

Determination of Optimal Clinical Target Volume to Planning Target Volume Margins for Conformal Radiotherapy Planning using Image Guidance System in Rectal Cancer in Prone Position.

CONTEXT: In advanced radiotherapy techniques such as three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT), geometrical uncertainties are very crucial as they may lead to under dosing of tumor and over dosing of the nearby critical structures and hence, it is important to determine planning target volume (PTV) margins which are specific for every center. AIMS: The aim of this study is to determine adequate clinical target volume (CTV) to PTV margins specific to our radiotherapy center. SETTINGS AND DESIGN: To calculate CTV to PTV margins for rectal cancer patients in prone position using kV cone beam CBCT data sets. MATERIALS AND METHODS: With the Patient immobilized in prone position using thermoplastic mask, a CT simulation was done and a comprehensive 3DCRT plan was generated. Daily kV CBCT was done to check the patient setup error. Daily setup errors were recorded and evaluated retrospectively. RESULTS: CTV-PTV margin calculated for pelvis in the prone position was calculated using van Herk Formula and were found to be 0.5, 1.8, 0.7 cm in the lateral, longitudinal, and vertical directions, respectively. CONCLUSIONS: Image guidance is an effective method to evaluate patient setup errors. Good quality immobilization devices and stringent patient setup policies can help to reduce PTV margins further.

Ligand assisted electrocatalytic water oxidation by a copper(ii) complex in neutral phosphate buffer.

The electrocatalytic water oxidation activity of a copper(ii) complex, 1, [Cu(L1H)(L1)(OH2)](ClO4), with a redox active aryl oxime ligand, L1H [L1H = 1-(pyridin-2-yl) ethanone oxime] has been investigated. Complex 1 shows a remarkably high turnover frequency of ∼100 s-1 in neutral phosphate buffer at about 675 mV overpotential with ∼94% faradaic efficiency. Electrochemical analysis suggests the involvement of a ligand moiety in a proton-coupled-electron-transfer (PCET) step during the catalytic cycle of complex 1, which in turn provides a route for accumulation of high oxidizing equivalents at the reaction center.

Evaluation of hypopharyngeal carcinoma using high-resolution ultrasound: comparison with CT.

BACKGROUND: To evaluate the role of sonography (US) in assessing hypopharyngeal carcinoma when compared with CT. METHODS: A randomized prospective study was performed on 40 biopsy-proven cases of hypopharyngeal carcinoma.Contrast-enhanced CT of the neck was performed in all patients, followed by US. Sonographic identification of any tumor extension into the extralaryngeal soft tissues, postcricoid space, subglottis, thyroid gland, esophagus, and across the midline was recorded. US observations and CT findings were compared and then correlated with the histopathologic findings in 14 operative cases. In the remaining 26 inoperable cases, US was compared only with CT. RESULTS: Our cohort was composed of 38 men and 2 women ranging in age from 36 to 59 years. In a subset of 14 operative patients, US had a sensitivity of 71.4% (10/14), while CT achieved a sensitivity of 92.8% (13/14), and the difference was not statistically significant (p > 0.05). US and CT findings concurred in 67.5% (27/40) of cases. CONCLUSIONS: Even though small tumors are difficult to visualize, US can play a significant role in the assessment of tumor extension within and beyond the larynx, especially when cross-sectional imaging is either unavailable or unaffordable.

Reaction of a copper(II)-nitrosyl complex with hydrogen peroxide: phenol ring nitration through a putative peroxynitrite intermediate.

Copper(II) complex, 1, with the histidine-derived ligand L (L = methyl 2-(2-hydroxybenzylamino)-3-(1H-imidazol-5-yl)propanoate) has been synthesized and characterized. Single-crystal structure determination reveals a diphenolato-bridged dicopper(II) core in 1. Addition of (•)NO to an acetonitrile solution of 1 affords the corresponding mononuclear copper(II)-nitrosyl complex, 2. In the presence of H2O2, 2 results in formation of the corresponding copper(I)-peroxynitrite. Formation of peroxynitrite ((-)OONO) intermediate is evident from its characteristic phenol ring nitration reaction which resembles the tyrosine nitration in biological systems. Further, isolation of nitrate (NO3(-)) as the decomposition product from 2 at room temperature also supports the involvement of (-)OONO intermediate.

Nested multiplex PCR based detection of human papillomavirus in cervical carcinoma patients of North- East India.

BACKGROUND: Persistent infection of one or more of about 15 high-risk human papillomaviruses (HR-HPVs), most commonly HPV types 16/18, has a significant role in cervical cancer initiation and progression. There are limited data available from north-east India about HPV prevalence though this region has high incidence rates of cervical cancer. The aim of this study was to investigate the HPV genotypes prevalent in cervical cancer patients of north-east India. MATERIALS AND METHODS: We analyzed 107 cervical cancer patient samples. Nested multiplex PCR assays were employed for detection of 13 high risk and 5 low risk HPV types. RESULTS: HPV was confirmed in 105 samples. The presence of 6 'carcinogenic' HPV types, HPV-16 (88%), -18 (15%), -31(4%) ,-45 (3%), -59 (4%), -58(1%), and one non carcinogenic, HPV-6/11 (6%), was recorded. Among various demographic and clinical factors only tumour stage showed a statistically significant association with HPV type infection (P=0.019). CONCLUSIONS: We suggest that the most prevalent genotype is HPV-16 followed by HPV-18 in cervical carcinoma patients of the north-eastern region of India. Advanced tumour stage may be associated with increased possibility of harbouring multiple HPV genotypes.

Nitric oxide reactivity of Cu(II) complexes of tetra- and pentadentate ligands: structural influence in deciding the reduction pathway.

Four Cu(II) complexes, 1, 2, 3 and 4, are synthesized with ligands, L1, L2, L3 and L4 [L1 = N1,N2-bis((pyridin-2-yl)methyl)ethane-1,2-diamine; L2 = N1,N3-bis((pyridin-2-yl)methyl)propane-1,3-diamine; L3 = N1,N1,N2-tris((pyridin-2-yl)methyl)ethane-1,2-diamine; L4 = N1-((1-methyl-1H-imidazol-2-yl)methyl)-N1,N2-bis((pyridin-2-yl)methyl)ethane-1,2-diamine], respectively, as their perchlorate salts. The complexes were characterized by various spectroscopic techniques as well as single crystal X-ray structure determination. Nitric oxide reactivities of the complexes were studied in acetonitrile as well as methanol solvent. It has been found that the ligand frameworks have a considerable effect in controlling the mechanism of the reduction of a Cu(II) center by nitric oxide. The flexibility of the ligand/s for a Cu(II) complex to attain a trigonal bipyramidal geometry after NO coordination is found to be the most important parameter in dictating the pathway for their interaction. In the present study, all the four compounds, because of structural constraints, were found to follow a deprotonation pathway for the reduction of a Cu(II) center by nitric oxide rather than [Cu(II)-NO] intermediate formation. All the ligands were found to yield an N-nitrosoamine product along with the reduction of Cu(II) centers by nitric oxide.

Copper(II) complexes as turn on fluorescent sensors for nitric oxide.

Two copper(II) complexes, 1 and 2, of two tridentate N-donor ligands, L(1) and L(2) [L(1) = dansyl derivative of bis-[3-(dimethylamino)-propyl]amine; L(2) = dansyl derivative of dipropylenetriamine] were synthesized and characterized. The quenched fluorescence intensity of complexes 1 and 2, in degassed methanol or aqueous (buffered at pH 7.2) solution, was found to reappear on exposure to nitric oxide. This is attributed to the reduction of paramagnetic Cu(II) center by nitric oxide to diamagnetic Cu(I).

Reaction of a copper(II)-nitrosyl complex with hydrogen peroxide: putative formation of a copper(I)-peroxynitrite intermediate.

The reaction of a Cu(II)-nitrosyl complex (1) with hydrogen peroxide at -20 °C in acetonitrile results in the formation of the corresponding Cu(I)-peroxynitrite intermediate. The reduction of the Cu(II) center was monitored by UV-visible spectroscopic studies. Formation of the peroxynitrite intermediate has been confirmed by its characteristic phenol ring nitration reaction as well as isolation of corresponding Cu(I)-nitrate (2). On air oxidation, 2 resulted in the corresponding Cu(II)-nitrate (3). Thus, these results demonstrate a possible decomposition pathway for H(2)O(2) and NO through the formation of a peroxynitrite intermediate in biological systems.

First example of a Cu(I)-(η2-O,O)nitrite complex derived from Cu(II)-nitrosyl.

Copper(II) complex, 1, of the bidentate ligand, L [L = bis(2-ethyl-4-methyl-imidazol-5yl)methane] has been synthesized and structurally characterized. Addition of nitric oxide gas to a degassed acetonitrile solution of 1 yielded the corresponding copper(ii)-nitrosyl complex, 2. In acetonitrile, complex 2 on reaction with water afforded the corresponding copper(I)-nitrite complex, 3. Single crystal structure of complex 3 reveals the bidentate nitrite (η(2)-O,O) bonding. This is the first example of a structurally characterized Cu(I)-(η(2)-O,O)nitrite complex with N-donor ligand. The sequence of the formation of these complexes is just the reverse of the key steps of the postulated nitrite reduction cycle by CuNiRs.