Solvatochromism and estimation of ground and excited state dipole moments of 6-aminoquinoline.

The spectral behaviour of 6AQ was investigated using fluorescence spectroscopy in several polar and non-polar solvents. Both the absorption and fluorescence spectra displayed solvatochromism. The Stokes shift increased significantly with increasing solvent polarity and signifies a more polar excited state with possible change in the excited state (ES) geometry. The involvement of π→π∗ transition was observed. The ground state (GS) and excited state (ES) dipole moments were determined by the solvatochromic shift method using Bilot-Kawaski, Lippert-Mataga, Kawski-Chamma-Viallet, and Reichardt equations. The experimental value of GS dipole moment matches closely with the theoretical value computed using DFT/B3LYP/6-311G(d,p). The ES dipole moment is higher than the GS dipole moment. Besides, the solvatochromic study reveals that the ES of 6AQ is more polarized than the GS due to intramolecular charge transfer (ICT), possibly aided by a change in the geometry of the molecule in the ES. The influence of the non-specific and specific interactions in the photophysical properties of the titled molecule was analyzed using the Catalan scale. The study shows that 6AQ has reasonable band-gap energy and good CIE chromaticity coordinate in the blue region close to the national television standard committee system (NTSC) for the ideal blue CIE coordinate. Therefore, future research into 6AQ as a source of light-emitting diodes and fluorescent sensors may have potential applications in the field of optoelectronics.

Structural, Electronic and NLO Properties of 6-aminoquinoline: A DFT/TD-DFT Study.

A computational study based on the DFT/TD-DFT approach was performed to explore various properties of 6-aminoquinoline (6AQ). The geometrical parameters, molecular orbitals (MOs), electronic spectra, electrostatic potential, molecular surface, reactivity parameters and thermodynamic properties of 6AQ were explored. The absorption and emission spectra of 6AQ in solvents have been estimated by TD-DFT coupled with the PCM model and correlated with the available experimental results. Depending on the solvents, the computed absorption maxima of 6AQ were noticed between 327 nm - 340 nm and ascribed to [Formula: see text] transition. The simulated emission maxima were obtained between 389 to 407 nm and ascribed to [Formula: see text] transition. On increasing the solvent polarity, both the emission and absorption maxima showed a bathochromic shift. The LUMO and HOMO were localized on the entire molecule. It was observed that the lowest excited state is possibly the [Formula: see text] charge-transfer (CT) state. The natural bonding orbital (NBO) study points out that ICT plays a significant role in stabilizing the molecular system. Moreover, the NLO (nonlinear optical) properties (polarizability, first-order hyperpolarizability and dipole moment) were computed using different hybrid functionals. The estimated values indicate that 6AQ can be considered a desirable molecule for further studies of the NLO applications.

Are patients with primary hypothyroidism in India receiving appropriate thyroxine replacement? An observational study.

BACKGROUND: A large proportion of patients worldwide under treatment for hypothyroidism with thyroxine show suboptimal Thyroid Stimulating Hormone (TSH) values. There is a paucity of Indian data on 'out-of-range' TSH values in patients with primary hypothyroidism receiving levothyroxine treatment. AIM: To assess the percentage of primary hypothyroid patients with abnormal thyroid function despite being prescribed levothyroxine for at least 2 m. MATERIALS AND METHODS: A cross-sectional, single visit, observational study in adult patients with primary hypothyroidism on treatment with levothyroxine for at least 2m was undertaken across 10 cities in India. Compliance to thyroxine therapy was assessed by interviewing the subjects and their quality of life was assessed by administering the SF-36 questionnaire. A random blood sample (5ml) was drawn from the study subjects during the same visit for assessing serum TSH levels. TSH levels were correlated with the current dose of levothyroxine. RESULTS: A total of 1950 subjects (mean age 41.4 ± 11.17 years; female 81.2%, male 18.8%) with primary hypothyroidism were enrolled in the study. Of the 1925 subjects in whom TSH values were available, 808 (41.97%) were under-treated (TSH > 4 mIU/L) and 243 (12.62%) were over-treated (TSH < 0.4mIU/L). The mean dose of thyroxine in this study was 1.23 µg/kg/day (±0.85). Majority of subjects (90.79%) were compliant/moderately compliant to thyroxine therapy. Age and autoimmune hypothyroidism were the factors that had significant impact on serum TSH. Subjects with abnormal TSH had significantly lower scores for role limitation due to emotional problems (P = 0.0278) and due to physical health (P = 0.0763). CONCLUSION: This study concluded that around half (54%) of known hypothyroid subjects had out-of-range serum TSH despite being treated with levothyroxine for at least 2m. The mean daily dose of thyroxine (1.23 µg/kg ± 0.85) was less than the recommended full replacement dose.

Prevalence of hypothyroidism in adults: An epidemiological study in eight cities of India.

BACKGROUND: Hypothyroidism is believed to be a common health issue in India, as it is worldwide. However, there is a paucity of data on the prevalence of hypothyroidism in adult population of India. MATERIALS AND METHODS: A cross-sectional, multi-centre, epidemiological study was conducted in eight major cities (Bangalore, Chennai, Delhi, Goa, Mumbai, Hyderabad, Ahmedabad and Kolkata) of India to study the prevalence of hypothyroidism among adult population. Thyroid abnormalities were diagnosed on the basis of laboratory results (serum FT3, FT4 and Thyroid Stimulating Hormone [TSH]). Patients with history of hypothyroidism and receiving levothyroxine therapy or those with serum free T4 <0.89 ng/dl and TSH >5.50 µU/ml, were categorized as hypothyroid. The prevalence of self reported and undetected hypothyroidism, and anti-thyroid peroxidase (anti-TPO) antibody positivity was assessed. RESULTS: A total of 5376 adult male or non-pregnant female participants ≥18 years of age were enrolled, of which 5360 (mean age: 46 ± 14.68 years; 53.70% females) were evaluated. The overall prevalence of hypothyroidism was 10.95% (n = 587, 95% CI, 10.11-11.78) of which 7.48% (n = 401) patients self reported the condition, whereas 3.47% (n = 186) were previously undetected. Inland cities showed a higher prevalence of hypothyroidism as compared to coastal cities. A significantly higher (P < 0.05) proportion of females vs. males (15.86% vs 5.02%) and older vs. younger (13.11% vs 7.53%), adults were diagnosed with hypothyroidism. Additionally, 8.02% (n = 430) patients were diagnosed to have subclinical hypothyroidism (normal serum free T4 and TSH >5.50 µIU/ml). Anti - TPO antibodies suggesting autoimmunity were detected in 21.85% (n = 1171) patients. CONCLUSION: The prevalence of hypothyroidism was high, affecting approximately one in 10 adults in the study population. Female gender and older age were found to have significant association with hypothyroidism. Subclinical hypothyroidism and anti-TPO antibody positivity were the other common observations.

Steady state and time-resolved fluorescence study of isoquinoline: reinvestigation of excited state proton transfer.

In the present work we report some hitherto unnoticed features in the steady state and time-resolved measurements of isoquinoline in water and trifluoroethanol (TFE). Absorption spectra reveal that in water, neutrals as well cationic species are present. Emission spectrum shows structured features at shorter wavelengths accompanied with a broad band around 375 nm, which correspond to neutrals and cations respectively. However, time-resolved data indicate that protonation does not take place in the excited state in water. On the contrary, in stronger hydrogen bonding solvent TFE, distribution of decay components is observed and at longer wavelengths a small rise time is present. This is ascribed to neutral and cation-like species present in the ground as well as in the excited state. The difference in the results is explained in terms of different excited state potential energy surfaces for water and TFE; particularly, the presence of a rather small barrier for protonation in case of TFE.