COVID-19-Related Fear and Mental Distress Among Tunisian Primary, Middle and High School Teachers: Prevalence and Predictive Factors.

This study aimed to determine the prevalence and predictive factors of fear of COVID-19 and serious mental distress among teachers in public schools of Southern Tunisia. This was a cross sectional study among a representative sample of 525 teachers. The level of Fear was assessed using the Fear of COVID-19 Scale (FCV-19S). A high level was defined as an FCV-19S ≥ 22. Kessler 6 (K6) was performed to predict serious mental distress. Serious mental distress was defined as a K6 score ≥ 13. The prevalence rates of high level of fear of COVID-19 and serious mental distress were 32.8% and 63.8%, respectively. Independent factors associated with a high level of fear of COVID-19 were female gender (Adjusted odds ratio (AOR)=1.6 [1.1-2.5]), chronic disease (AOR=1.6 [1.1-2.4]), home-living children (AOR=3.3 [1.4-7.8]), and poor material working conditions (AOR=1.5 [1.2-2.1]). The high level of fear of COVID-19 (AOR=3.1 [1.8-5.1]) was independently associated with serious mental distress. Living in a rural area (AOR=0.4 [0.3-0.8]), previous COVID-19 infection (AOR=0.5 [0.4-0.8]) and going to school on foot (AOR=0.3 [0.2-0.51]) were independently associated with a lower prevalence of serious mental distress.

Effectiveness of a Training Intervention about Healthcare Waste Management on the Knowledge and Practical Skills of Healthcare Professionals in a Teaching Hospital of Southern Tunisia.

This quasi-experimental study aimed to assess the impact of a training program on knowledge and practical skills of healthcare professionals(HCPs) regarding healthcare waste(HCW) management in a Teaching Hospital in Southern Tunisia.The total mean knowledge score(KS) and practice score(PS) increased significantly on post training test as opposed to pre-training test with mean changes of 17.9 ± 10.1 and 26.9 ± 2.1, respectively.The mean PS did not significantly change from the first to the final follow-up measurement(p = 0.25).Three predictor factors were found to be independently associated with change in KS:age(ß=-0.16;p = 0.006),sanitary staff(ß = 0.116;p = 0.038) and administrative staff(ß = 0.122;p = 0.032).Training program could therefore be an effective intervention for improving knowledge and practices among HCPs.

Adverse effects of personnel protective equipment among first line COVID-19 healthcare professionals: A survey in Southern Tunisia.

BACKGROUND: Health care professionals (HCP) were obliged to wear personal protective equipment (PPE) during pandemic in order to minimize the risk of transmission of the emerging virus. The objective of the study was to estimate the prevalence of adverse effects related to the wear of PPE among HCP and to determinate their predictive factors. METHODS: This was a cross-sectional study including a representative sample of 300 randomized HCP at Hedi Chaker University Hospital Sfax, Tunisia, during the period August-September 2021. Data collection was carried out by an anonymous self-administered questionnaire. RESULTS: PPE related adverse effects were noted among 87 HCP with a prevalence of 57.2%. Multivariate analysis showed that factors independently associated with PPE adverse effects were female gender (Adjusted Odds Ratio (AOR) = 1.8; p = 0.048), chronic diseases (AOR = 0.29; p = 0.001) and previous infection with COVID-19 (AOR = 0.46; p = 0.004). Frequent use of bleach or other disinfection product without protection and use of hot water at work were independently associated with a high risk of adverse effects ((AOR = 2.22; p = 0.003) and (AOR = 2.83; p = 0.005), respectively). Similarly, a duration of use of PPE>4 h per day (AOR = 1.98; p = 0.039), as well as use of visors and/or glasses (AOR = 1.84; p = 0.045) were independently associated with PPE related adverse effects. CONCLUSION: The prevalence of adverse effects related to the wear of PPE was alarmingly high among HCP. Multiple risk factors were highlighted, notably professional aspects. Adequate and repetitive training for caregivers on the correct use of PPE remain essential to manage this problem.

Prevalence and Factors Affecting Willingness to Accept or Refuse Vaccination against COVID-19 among Healthcare Professionals in Southern Tunisia.

BACKGROUND: The COVID-19 pandemic continues to spread throughout the world causing serious morbidity and mortality. Health care professionals (HCP) are on the front line in the face of this pandemic and are identified as priorities for COVID-19 vaccination. This study aimed to estimate the acceptability rate of the COVID-19 vaccination among HCP and to identify their predisposing factors. Methods: This was a cross-sectional study using an anonymous self-administered questionnaire including a randomized sample of HCP in Southern Tunisia, on March-April 2021. Results: Among 300 participants, the COVID-19 vaccine acceptability rate was 65.3%. Factors independently associated with vaccine acceptability were age groups <30 years [Adjusted Odds Ratio (AOR)=4.36; p = 0.002)], urbanity of residence (AOR = 3.44; p = 0.027), medical professional category (AOR = 2.69; p = 0.023) and caring for coronavirus infected patients (AOR = 2.32; p = 0.047). Belief that COVID-19 vaccination is important to work safely as a health care provider (AOR = 3.26; p = 0.013), should be available for all HCP (AOR = 17.98; p = 0.004) and has been quickly developed before it has been thoroughly vetted and tested for efficacy and safety (AOR = 5.88; p < 0.01) were independently associated with willingness to accept vaccine. Planning to get a COVID-19 vaccine for the next years and recommending it to the family were independent predictive factors of accepting COVID-19 vaccine ((AOR = 6.88; p < 0.001) and (AOR = 25.03; p < 0.001), respectively).Conclusion: The acceptance rate of vaccination against COVID-19 among Tunisian HCP is still low in South Tunisian hospitals. Socio-demographic, cultural and professional factors predisposing to the vaccination willingness were highlighted. Combating the vaccine hesitancy of HCP through enhancing sensibilization campaigns is essential to promote vaccination in general population.

Bone marrow aspirate: a diagnostic tool for primary hyperoxaluria type 1.

INTRODUCTION: Type1 primary hyperoxaluria is an infrequent autosomal recessive metabolic disease characterized by the accumulation of calcium oxalate in the kidney, which leads to end stage renal disease. In fact, the diagnosis of this disease is mandatory in order to avoid graft loss. AIM: To assess the incidence of primary hyperoxaluria and to develop the diagnostic value of bone marrow infiltration by calcium oxalate in uremic stone former patients. METHODS: This study was conducted on a cohort of stone former patients identified in the south of Tunisia over a period of 18 years. Baseline characteristics were recorded. Clinical and laboratory data were collected on chart review. Secondary forms of hyperoxaluria were excluded. Bone marrow aspirate was performed in uremic patients from this cohort because early hyperoxaluria was suspected. Diagnostic accuracy of this test relating to sensitivity, specificity, positive predictive value and negative predictive value were also calculated. RESULTS: A cohort of 31 patients comprising 17 male patients and 14 female patients were identified. During this time of diagnosis, the patient's ages ranged from 9 to 57 years old and 22 of them (70%) unfortunately died. Bone marrow aspirate was safely done in 16 uremic patients. It was positive in 12 patients and negative in 4 patients. Sensitivity, specificity, positive predictive value and negative predictive value were respectively 85%, 100%, 100% and 50%. CONCLUSION: The bone marrow examination represents both an easy and a worldwide feasible solution for the diagnosis of oxalosis, which affords an early diagnosis.

Epidemiological profile and performance of triage decision-making process of COVID-19 suspected cases in southern Tunisia.

INTRODUCTION: During an epidemic, screening processes can play a crucial role in limiting the spread of the infection. The aim of this study was to describe the epidemiological profile of COVID-19 suspected cases and to evaluate the performance of the triage process in predicting COVID-19 in Southern Tunisia. METHODS: It was a prospective study including all patients consulting to the Hedi Chaker University Hospital departments from March to June 2020. A clinical triage score (CTS) was used to assess the risk of the infection and to refer patients to the appropriate part of the facility accordingly. RESULTS: Overall, 862 patients were enrolled, among whom 505 patients (58.6%) were classified as suspected cases (CTS ≥4). Of these, 46.9% (n = 237) were of mild form. Samples were collected from 215 patients (24.9%), among whom five were COVID-19 positive, representing a positive rate of 2.3%. The in-hospital cumulative incidence rate of COVID-19 was 580/100000 patients. The total daily incidence decreased significantly during the study period (p < 0.001, chi-square for linear trend = 25.6). At a cut-off of four, the CTS had a sensitivity of 40%, a specificity of 32.4%, and negative and positive predictive values of 95.8% and 1.4%, respectively. DISCUSSION: Although the triage process based on the CTS was not as performant as the RT-PCR, it was crucial to interrupt virus spread among hospitalized patients in "COVID-19-free departments".

Prevalence, chronological trends and predictors of treatment outcomes among patients with tuberculosis in Southern Tunisia across two decades (1995-2016).

INTRODUCTION: Tuberculosis (TB) is a communicable disease common worldwide. Influencing factors in TB outcomes include socio-demographics, as well as disease-related and treatment-related factors. This study aimed to analyze the prevalence trends of unsuccessful treatment outcomes in Southern Tunisia during 1995-2016 and to identify their risk factors. METHODS: This was a retrospective study including all notified cases from the tuberculosis center reporting registers in Southern Tunisia between 1995 and 2016. RESULTS: Overall, 2771 TB cases were notified. Unsuccessful treatment outcomes were noted in 196 cases (7%). Unsuccessful treatment outcome was associated with male gender (OR=1.4; p=0.023), elderly status (≥60 years, OR=2.3; p<0.001), joints and bones site (OR=2.2; p=0.002) as well as meningeal involvement (OR=2.4; p=0.023). Lymph node (OR=0.4; p<0.001) and therapy duration ≥6 months (OR=0.003; p<0.001) were statistically associated with lower rate of unsuccessful outcome. Multivariate regression analysis showed that elderly status (AOR=2.3; p<0.001), meningeal involvement (AOR=2.2; p<0.027) as well as bone and joints involvements (AOR=2; p=0.027) were independently associated with unsuccessful outcome. Trends analysis showed that the case-fatality rate significantly increased from 1995 to 2016 (Rho=0.4; p=0.032). CONCLUSIONS: The high prevalence of unsuccessful outcome suggested important inadequacies in the TB program. An effective strategy to improve therapeutic education of patients with TB is therefore urgently needed.

Point prevalence survey of health-care associated infections and their risk factors in the tertiary-care referral hospitals of Southern Tunisia.

BACKGROUND: Health-care associated infections (HAI) are considered a public health problem and have substantial effect on mortality and morbidity. This study aimed to determine the prevalence of HAI in South Tunisian University Hospitals (UH) and to identify their risk factors. METHODS: We performed a point prevalence study, in the UH of Southern Tunisia in February 2019, including all hospitalized patients for at least 48 hours. RESULTS: Overall, 898 patients were included in this survey, among whom 480 participants (53.5%) were males. There were 81 HAIs, accounting for a prevalence of HAI of 9.02%. Urinary tract infections (28.4%) were the most common HAI, followed by respiratory tract infections (22.2%). The main identified microorganisms among HAI patients were Klebsiella pneumonia (22.7%) and Escherichia coli (20.7%). Independent intrinsic risk factors of high prevalence of HAI were diabetes (Adjusted Odds Ratio (AOR)=3.5;p=0.016) having a rapidly fatal disease (AOR=4;p=0.024) and an ASA scores ≥2 (AOR=2.8;p=0.045). As for extrinsic risk factors, admission in ICU (AOR=11.1;p= 0.04), a length of hospital stay ≥ 7 days (AOR=4.1;p=0.04), previous hospitalization within 90 days prior to the admission (AOR=4.2;p=0.01) and having a peripheral vascular catheter (AOR=6.7; p=0.039) were independently associated with higher prevalence of HAI. Lower prevalence of HAI was independently associated with prescription of antimicrobial preoperative prophylaxis (AOR= 0.1; p=0.02). CONCLUSION: Our findings illustrated high prevalence of HAI in South Tunisian Hospitals, affecting principally fragilized patients who may require special needs. Therefore, promoting hygiene programs for health professionals to establish patient safety's culture is urgently needed.

Prevalence and factors associated with smoking among Tunisian secondary school-adolescents.

OBJECTIVES: This study aimed to estimate the extent of smoking experience among high and middle school adolescents in Southern Tunisia and to delineate its potential associated factors. METHODS: We conducted a cross-sectional study among middle and high school-adolescents in the governorate of Sfax, South of Tunisia in the 2017-2018 school-years. A questionnaire was anonymously administered to a representative sample of 1,210 school-adolescents randomly drawn. RESULTS: The mean age of the school-adolescents was 15.6 ± 4.2 years. The prevalence of lifetime smoking was 16.7% (95% CI=[14.7-18.8%]) (boys 32.6%; girls 5.9%;p<0.001). Among the respondents, 13.9% (95% CI=[11.9-15.8%]) were current smokers. In multivariate logistic regression analysis, independent associated factors of current smoking were male gender (Adjusted (AOR)=10.2; p<0.001), 16-17 and 18-19-year age-groups (AOR=2; p=0.005 and AOR=2.6; p=0.001, respectively), below average academic performance (AOR=5.2; p=0.012), divorced parents (AOR=3.9; p=0.007), family monthly income ≥800 dollars (AOR=2.1; p=0.001), having a part time job (AOR=3.9; p<0.001) and a perceived high stress level (AOR=1.98; p=0.008). Secondhand smoke (AOR=1.8; p=0.011) and concomitant alcohol drink (AOR=14.56; p<0.001) were independent predictors of current smoking, while high education level of the father was independently associated with lower prevalence of current smoking (AOR=0.17; p<0.001). CONCLUSION: The prevalence of lifetime and current smoking were relatively high in Southern Tunisian middle and high schools. Multilevel influences on youth smoking behavior had been identified, which reflected the need to conceive appropriate school interventions and effective antismoking education program.

[Non-communicable diseases in Southern Tunisia: morbidity, mortality profile and chronological trends] / Les maladies non-transmissibles au Sud tunisien : profil de morbi-mortalité et tendances chronologiques.

OBJECTIVES: Non-communicable diseases (NCDs) represent a major public health problem worldwide. Giving their impact on the morbidity and mortality burden, understanding their chronological trends over time is a priority for epidemiological surveillance. We aimed to determine the epidemiological specificities of NCDs and to study their chronological trends over the period 2010-2015. METHODS: We retrospectively collected data of hospitalized patients from the regional registry of morbidity and mortality in the Southern University Hospital of Tunisia during the period 2010-2015. RESULTS: We included 18,081 patients with NCDs aged ≥ 25 years. The distribution of NCDs was characterized by the predominance of cardiovascular disease (CVD) (10,346 cases, 57.2%). Chronological trends analysis of NCDs showed that NCDs remained globally stable between 2010 and 2015. The same result applied to the group of cancers, chronic respiratory diseases and diabetes mellitus. However, CVD increased significantly between 2010 and 2015 (ρ = 0.84; p = 0.036). The proportion of CVD increased significantly among men (ρ = 0.87; p = 0.019) and elderly (ρ = 0.88; p = 0.019). The hospital mortality rate of NCDs increased significantly (ρ = 0.85; p = 0.031), notably for CVDs (ρ = 0.94; p = 0.005). CONCLUSION: Chronological trends analysis revealed a significant rise in the morbidity and mortality burden of CVDs during the period 2010-2015. It is imperative, therefore, to strengthen health care for these patients and to introduce the concept of integrated NCDs prevention as an essential component of the health system.

What are the correlates of body image distortion and dissatisfaction among school-adolescents?

BACKGROUND: Body image is considered as central to many aspects of human functioning including emotions, thoughts, behaviors and relationships. Our study aimed to investigate the prevalence of body image distortion and dissatisfaction among adolescents and to assess their main determinants. METHODS: This was a cross-sectional school-based study conducted among school-adolescents in the south of Tunisia, between October 2017 and February 2018. RESULTS: Among 1210 school-adolescents, body image distortion and dissatisfaction prevalence were 44.8% and 42.4%, respectively. Multivariate analysis showed that being in the 16-18 years age group [adjusted odds ratio (AOR) = 1.28, p = 0.046], low family financial situation (AOR = 1.88, p = 0.014), as well as high frequency of eating pasta (AOR = 1.3, p = 0.04) and fast-food consumption (AOR = 1.7, p = 0.042) were independently associated with under-estimated body image. Skipping breakfast (AOR = 1.9, p = 0.017) and having one obese parent (AOR = 1.9, p = 0.01) were independently associated with higher frequency of over-estimated body image. Regarding body image dissatisfaction, independent factors associated with desire to lose weight were: female gender (AOR = 1.53, p = 0.007), high income family financial situation (AOR = 2.1, p = 0.008) and having one parent who is obese (AOR = 2.21, p < 0.001). However, frequent fast-food consumption (AOR = 1.9, p = 0.038) and eating between meals (AOR = 1.57, p = 0.01) were independently associated with a higher desire to gain weight. CONCLUSIONS: Our study highlighted that the prevalence of body image distortion and dissatisfaction were substantially high among adolescents. Their determinants included socio-demographic factors and lifestyle behaviors. Increased awareness among parents, educators and public health planners may help adolescents improve accuracy of body image attitudes.

Prevalence, Risk Factors and Outcomes of Neck, Shoulders and Low-Back Pain in Secondary-School Children.

BACKGROUND: Musculoskeletal pain (MSP) is a public health problem among school-adolescents. This study aimed to identify the prevalence, risk factors and consequences of neck, shoulders and low-back pain among school-adolescents. STUDY DESIGN: A cross-sectional study. METHODS: School-adolescents aged from 12 to 18 years between October 2017 and February 2018 in South of Tunisia were recruited. Eligible participants were randomly selected and were asked to respond a four-section questionnaire. Factors independently associated with MSP were determined through multivariate logistic regression analysis. RESULTS: Among 1221 enrolled subjects, shoulders, low-back and neck pain were reported in 43%, 35.8% and 32%, respectively. Multivariate analysis showed that independent risk factors of neck pain were female gender (Adjusted odds ratio AOR=1.55; P=0.002), using computer ≥4 hours/week (AOR=1.50; P=0.010), too low desk (AOR=2.30; P<0.001) and carrying schoolbag ≥60 minutes (AOR=1.58; P=0.008). Female gender (AOR=3.30; P<0.001), BMI ≥25 Kg/m2 (AOR=1.6; P=0.018), playing videogames ≥2 hours/day (AOR=2.37; P<0.001) and schoolbag weight to body weight ≥10% (AOR=1.46; P=0.026) were independently associated with shoulders pain. For low back-pain, independent risk factors were high-school grade (AOR=2.70; P<0.001), playing videogames ≥2 hours/day (AOR=1.83; P<0.001), watching TV≥12 hours/week (AOR=1.5; P=0.016), too low seat backrest (AOR=1.4; P=0.005) and too far seat-to-black (board) distance (AOR=1.5; P=0.041). School-adolescents consumed drugs for MSP in 19.5%, had sleep disturbance in 34% and aggressive behaviors in 22.8%. CONCLUSIONS: The prevalence of MSP was substantially high among school-adolescents and their associated risk factors included sociodemographic factors, leisure activities and classroom furniture. An ergonomic specific and behavior-based school program is urgently needed.

Prevalence and risk factors of health care-associated infections in a limited resources country: A cross-sectional study.

BACKGROUND: The aim of this study was to determine the prevalence of health care-associated infections (HAI) in our university hospitals (UH) and to delineate the risk factors associated with HAI. METHODS: We conducted a cross-sectional study in the 2 UH of Sfax, Tunisia on July 2017, including all patients hospitalized for at least 48 hours. It was a 1-day pass per department and a 1-week prevalence survey per UH. RESULTS: Of 752 patients eligible for the study, the total number of HAI was 82, representing an overall prevalence of HAI of 10.9%. Respiratory tract infections were the most prevalent HAI (36.6%). In multivariate analysis, intrinsic risk factors independently associated with HAI were immune-suppression (adjusted odds ratio (AOR) = 2.8; P < .001), diabetes (AOR = 2.2; P = .008), and malnutrition (AOR = 2.2; P = .019). Extrinsic risk factors were endotracheal intubation (AOR = 17; P = .01), transfer to another department (AOR = 9; P = .019), parental feeding (AOR = 7.2; P = .014), tobacco use (AOR = 6.3; P = .004), as well as surgical wound class contaminated or dirty (AOR = 6.3; P = .002), and peripheral venous catheter (AOR = 4.7; P = .006). CONCLUSIONS: Our study highlighted the magnitude of the HAI problem threatening the quality of care in Southern Tunisia. A wise identification of HAI risk factors may help health care workers to ascertain the avoidability of these infections.

Pediatric respiratory tract diseases: Chronological trends and perspectives.

BACKGROUND: The aim of this study was to describe the epidemiological profile of childhood respiratory tract diseases (RTD) in the region of Sfax, Tunisia, and to evaluate their trends over a 13 year period. METHODS: We conducted a retrospective study of all children hospitalized with RTD aged under 14 years. We collected data from the regional morbidity register of the university hospital of Sfax from 2003 to 2015. RESULTS: A total of 10 797 RTD patients were enrolled from 49 880 pediatric hospitalizations (21.7%). A male predominance was noted (60%). The median age was 8 months (IQR, 2-36 months). Acute bronchitis (AB) accounted for 53.8%, followed by asthma (15%), pneumonia (14%) and acute upper respiratory infection (AURI; 7.2%). The hospital incidence rate (HIR) of RTD was 34/10 000 inhabitants/year. It was 18.2; 5.07; 4.7 and 2.4/10 000 inhabitants for AB, asthma, pneumonia and AURI, respectively. We noted a significant increase in the HIR of RTD with an annual percentage change (APC) of 10.94% (P < 0.001); in the HIR of AB (APC, 5.27%; P < 0.001); and in asthma HIR (APC, 11.2%; P < 0.001). Otherwise, a significant decrease in AURI HIR was observed (APC, -8.8%; P < 0.001). AB lethality rate increased significantly, with an APC of 7.4% (P < 0.001). Projected trends analysis up to 2024 showed a significant rise in AB and in asthma, while AURI would significantly decrease. CONCLUSIONS: RTD continues to be a serious health problem over time in terms of morbidity and mortality. Preventive and curative strategies are needed urgently.

Crystal structure, vibrational studies, optical properties and DFT calculations of 2-amino-5-diethyl-aminopentanium tetrachlorocadmate (II).

Single crystals of a new organic-inorganic compound (C9H24N2) CdCl4 were grown by the slow evaporation technique and characterized by X-ray diffraction, infrared absorption Raman spectroscopy scattering, optical absorption, differential scanning calorimetry (DSC) analysis and dielectric measurements. The title compound belongs to the orthorhombic space group Pbca with the following unit cell parameters: a=11.397(7), b=13.843(4), c=22.678(5)Šand Z=8. In crystal structure, the tetrachlorocadmate anion is connected to organic cations through N-H⋯Cl hydrogen bonds. Theoretical calculations were performed using density functional theory (DFT) with the B3LYP/LanL2DZ level of theory for studying the molecular structure and vibrational spectra of the title compound. Good consistency is found between the calculated results and the experimental structure, IR, and Raman spectra. The detailed interpretation of the vibrational modes was carried out on the basis on our DFT calculations as primary source of assignment and by comparison with spectroscopic studies of similar compounds. The optical properties were investigated by optical absorption and show three bands at 300, 329 and 513 nm.

Crystal structure, vibrational spectra and non-linear optical properties of diethylenetriammonium hexabromobismuthate: C4H16N3BiBr6.

A new organic-inorganic material, diethylenetriammonium hexabromobismuthate (C4H16N3)BiBr6, was synthesized and characterized by X-ray diffraction, infrared absorption, Raman spectroscopy scattering and optical absorption. The crystal lattice is composed of discrete [BiBr6] anions surrounded by diethylenetriammonium cations. The title compound crystallizes in the non-centro-symmetric space group P212121 of orthorhombic system. Theoretical calculations were performed using density functional theory (DFT) at B3LYP/LanL2DZ level of theory for studying the molecular structure, vibrational spectra and non-linear optical (NLO) properties of the investigated molecule in the ground state. Good consistency is found between the calculated results and the experimental structure, IR, and Raman spectra. The results also show that the title compound might have important NLO behavior and can be a potential new nonlinear optical (NLO) material of interest.

Molecular structure, NLO, MEP, NBO analysis and spectroscopic characterization of 2,5-dimethylanilinium dihydrogen phosphate with experimental (FT-IR and FT-Raman) techniques and DFT calculations.

Single crystals of 2,5-dimethylanilinium dihydrogen phosphate were grown by slow evaporation method at room temperature. The synthesized compound was characterized by powder X-ray diffraction analysis to confirm its crystalline nature. The optimized molecular structure, vibrational spectra and the optical properties were calculated by the density functional theory (DFT) method using the B3LYP function with the 6-31G(d,p) basis set. Theoretical simulation of infrared and Raman spectra led to excellent overall agreement with the observed spectral patterns. The complete assignments of the vibrational spectra were carried out with the aid of potential energy distribution (PED). The stability of the molecule arising from hyperconjugative interaction and charge delocalization has been analyzed using natural bond orbital (NBO) analysis leading to high nonlinear optical (NLO) activity. The lowering in the HOMO and LUMO energy gap explains the eventual charge transfer interactions that take place within the molecules.

Structural, vibrational and thermal studies of a new nonlinear optical crystal tetrapropylammonium dihydrogenmonoarsenate bis arsenic acid.

Single crystals of tetrapropylammonium dihydrogenmonoarsenate bis arsenic acid [CH3CH2CH2]4N (H2AsO4) (H3AsO4)2, a potential new nonlinear optical (NLO) material of interest were prepared by the slow evaporation technique and characterized by means of single-crystal X-ray diffraction, thermal analysis, FT-IR and Raman spectroscopy. The title compound belongs to the monoclinic space group Ia with the following unit cell dimensions: a=8.116(2) Ǻ, b=33.673(4) Ǻ, c=8.689(2) Ǻ, ß=95.34(2)°. The structure consists of infinite parallel two-dimensional planes built of mutually [H2AsO4(-)] and [H3AsO4] tetrahedra connected by strong O-H⋯O hydrogen bonding giving birth to trimmers. The planes of inorganic groups are alternated with those of the organic cations. The geometry, first hyperpolarizability and harmonic vibrational wavenumbers were calculated by means of density functional theory DFT with the B3LYP/6-31G(d) level of theory. Good consistency was found between the calculated results and the experimental structure, IR, and Raman spectra. The detailed interpretation of the vibrational modes was carried out building on the proposed DFT calculations as primary source of assignment and by comparison with the spectroscopic studies of similar compounds. The first hyperpolarizability ßtot of the title compound is about 14.6 times more than that of the reference crystal KDP, which may explain the importance of the compound under study.

Vibrational spectroscopic study, charge transfer interaction and nonlinear optical properties of L-asparaginium picrate: a density functional theoretical approach.

Single crystals of L-asparaginium picrate (LASP) were grown by slow evaporation technique at room temperature and were the subject of an X-ray powder diffraction study to confirm the crystalline nature of the synthesized compound. FT-IR and Raman spectra were recorded and analyzed with the aid of the density functional theory (DFT) calculations in order to make a suitable assignment of the observed bands. The optimum molecular geometry, normal mode wavenumbers, infrared and Raman intensities and the first hyperpolarizability were investigated with the help of B3LYP method using 6-31G(d) basis set. The theoretical FT-IR and Raman spectra of LASP were simulated and compared with the experimental data. A good agreement was shown and a reliable vibrational assignment was made. Natural bond orbital (NBO) analysis was carried out to demonstrate the various inter and intramolecular interactions that are responsible for the stabilization of the title compound leading to high NLO activity. A study on the electronic properties was performed by time-dependent DFT (TD-DFT) approach. The lowering in the HOMO and LUMO energy gap explains the eventual charge transfer interactions that take place within the molecules.