Ultrafast Dynamics and Computational Studies on Diaminodicyanoquinodimethanes (DADQs)

Three diaminodicyanoquinodimethanes, 4-(R¹R²C)-1-[(NC)₂C]-C₆H₄ (R¹,R² = H₂N, <b>1</b>; R¹ = 3,5-Me₂-4-OCH₄H₆N–, R² = H₂N, <b>2</b>; R¹ = 3,5-Me₂-4-OCH₄H₆N–, R² = 4-Me-C₅H₉N, <b>3</b>), were investigated using carbon-13 NMR, steady-state, and ultrafast transient absorption and ultrafast fluorescence spectroscopies to unravel the unusual characteristics of this class of chromophores. Computed (GIAO)­B3LYP/6-31G* data for the zwitterions <b>1</b>–<b>3</b> using necessary solvation (PCM) models were shown to be in excellent agreement with observed structural and carbon-13 NMR data. The ground-state geometries of <b>1</b>–<b>3</b> contain a cationic methine group R¹R²C– twisted from the C₆H₄ ring and an anionic methine group (NC)₂C– in plane with the C₆H₄ ring in solution and solid state. The ¹³C chemical shifts of the peak corresponding to the methine carbon at the (NC)₂C– group of <b>1</b>–<b>3</b> are observed at 32.5–34.7 ppm, which are some 55 ppm upfield compared with the ¹³C chemical shift for the methine carbons in TCNQ, 1,4-[(NC)₂C]₂-C₆H₄. The decay of the excited state in diaminodicyanoquinodimethanes is fast and dominated by nonradiative processes on the picosecond time scale, which depends on the viscosity of the medium. The dynamics of the excited-state decay is therefore limited by conformational changes through an intramolecular twisting motion. This twisting motion is hindered by friction, which, in turn, also depends on the functional group size of the system. The dominant nonradiative pathways after excitation are due to twisted excited-state conformers according to TD-DFT computations

Ultrafast Dynamics and Computational Studies on Diaminodicyanoquinodimethanes (DADQs)

Three diaminodicyanoquinodimethanes, 4-(R1R2C)-1-[(NC)2C]-C6H4 (R1,R2 = H2N, 1; R1 = 3,5-Me2-4-OCH4H6N–, R2 = H2N, 2; R1 = 3,5-Me2-4-OCH4H6N–, R2 = 4-Me-C5H9N, 3), were investigated using carbon-13 NMR, steady-state, and ultrafast transient absorption and ultrafast fluorescence spectroscopies to unravel the unusual characteristics of this class of chromophores. Computed (GIAO)B3LYP/6-31G* data for the zwitterions 1–3 using necessary solvation (PCM) models were shown to be in excellent agreement with observed structural and carbon-13 NMR data. The ground-state geometries of 1–3 contain a cationic methine group R1R2C– twisted from the C6H4 ring and an anionic methine group (NC)2C– in plane with the C6H4 ring in solution and solid state. The 13C chemical shifts of the peak corresponding to the methine carbon at the (NC)2C– group of 1–3 are observed at 32.5–34.7 ppm, which are some 55 ppm upfield compared with the 13C chemical shift for the methine carbons in TCNQ, 1,4-[(NC)2C]2-C6H4. The decay of the excited state in diaminodicyanoquinodimethanes is fast and dominated by nonradiative processes on the picosecond time scale, which depends on the viscosity of the medium. The dynamics of the excited-state decay is therefore limited by conformational changes through an intramolecular twisting motion. This twisting motion is hindered by friction, which, in turn, also depends on the functional group size of the system. The dominant nonradiative pathways after excitation are due to twisted excited-state conformers according to TD-DFT computations

Geoeconomic variations in epidemiology, ventilation management, and outcomes in invasively ventilated intensive care unit patients without acute respiratory distress syndrome: a pooled analysis of four observational studies

Background: Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. Methods: In this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middle-income countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality. Findings: Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42·4% vs 44·2%; absolute difference -1·69 [-9·58 to 6·11] p=0·67; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5-8] vs 6 [5-8] cm H2O; p=0·0011). ICU mortality was higher in MICs than in HICs (30·5% vs 19·9%; p=0·0004; adjusted effect 16·41% [95% CI 9·52-23·52]; p&lt;0·0001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0·80 [95% CI 0·75-0·86]; p&lt;0·0001). Interpretation: Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status