Elucidation of the hydration pattern of trifluoroacetic acid in dilute solutions: FTIR and computational study.

The atmospheric partitioning of trifluoroacetic acid (TFA) in aerosol is a complex function of the size of suspended water droplets and their pH value. The unraveling of the affinity of TFA towards basic but not acidic conditions may be accomplished by providing an insight into the hydration pattern of undissociated TFA. Owing to rather scarce details on very dilute aqueous solutions of trifluoroacetic acid (TFA), we examined CF3COOD and CF3COONa solutions in D2O in the concentration range 0.001-0.1 mol dm-3 using transmission FTIR spectroscopy and computational methods. Besides detecting the signals originated from undissociated species in both CF3COOD (1787 cm-1 and 1766 cm-1 at c0 = 0.1 mol dm-3) and CF3COONa (1807 cm-1 at c0 = 0.1 mol dm-3) D2O solutions, through computational techniques we identified different TFA hydrates that contribute to the complexity of the spectral appearance. The combination of experimental and computational data suggested the concentration dependence of the predominant hydrogen bonding pattern of TFA. The results obtained in this work should help in understanding the partitioning of TFA into micron-size water droplets in the atmosphere in molecular and structural terms, i.e. the eventual stability of a hydrated complex for a particular TFA conformer.

Effects of a prenatal anxiety randomized controlled trial intervention on infant development in Pakistan.

OBJECTIVES: Given that infant development is influenced by caregiver mental health, we tested whether an intervention to reduce antenatal anxiety could affect infant development. A secondary aim was to test depressive symptoms, maternal responsiveness, and maternal infant bonding as mediators of this relationship. METHODS: Between 2020 and 2022, pregnant women participated in a randomized controlled trial of the Happy Mother-Healthy Baby (HMHB) program based on cognitive behavioral therapy. We collected data on child development from 202 intervention and 198 control participants in a public hospital in Pakistan. Child development was measured using the Ages and Stages Questionnaires-Version 3 at six weeks postpartum. Using intent-to-treat analyses, we examined whether the intervention was associated with performance on the five ASQ-3 domains. Causal mediation analysis was used to assess depressive symptoms, bonding, and maternal-infant responsiveness as mediators. RESULTS: Socio-demographic characteristics were evenly distributed between study arms. Intervention arm infants showed a 2.1-point increase (95% CI: 0.12, 4.17) in communication scores compared to controls. Though not achieving statistical significance, intervention infants also showed a 2.0-point increase (95% CI:-0.06, 4.09) in gross motor development performance. Bonding, depression, and responsiveness were mediators between the intervention and infant communication (Bindirect=1.94 (95%CI: 0.86, 3.25) depression; Bindirect=0.57 (95% CI: 0.09, 1.16) bonding; Bindirect=0.53 (95% CI: 0.01, 1.21) responsiveness; and Bindirect=1.94 (95%CI: 0.86, 3.25). Bonding, responsiveness, and depression mediated 25%, 23%, and 87% of the total association, respectively. CONCLUSIONS: HMHB positively affected infant communication at six-week follow-up. Larger studies with longer follow-up are needed to confirm and extend these findings. TRIAL REGISTRATION: ClinicalTrials.gov NCT03880032; https://clinicaltrials.gov/ct2/show/NCT03880032.

A difference in application time between two direct orthodontic bonding methods: A prospective randomized clinical trial.

OBJECTIVE: This clinical study aimed to evaluate the difference in the time of application phase, employing the conventional and modified direct orthodontic bonding method. MATERIALS AND METHODS: Thirty patients who needed orthodontic therapy with fixed appliances were randomly divided into two equal groups (n = 15): the control and experimental group, according to the bonding method applied. A total of 600 metal brackets inch slot 0.022 (Mini Sprint®, Forestadent, Germany) were bonded to incisors, canines, and premolars using the light-cured adhesive Transbond XT (3M Unitek, Monrovia, CA, USA). The failure rates of the brackets were evaluated within 12 months. The independent samples t-test was applied. The Chi-square test and Fisher exact test were used for statistical analysis. RESULTS: The initial bonding time using the modified method was significantly shorter (3.27 min or 17.1% per patient) compared with the conventional bonding method (p < 0.001). Number of failed brackets between the two methods did not differ significantly (p = 0.226). CONCLUSION: The time of the application phase in initial bonding using the modified method (experimental group) was shorter than in control group. There was no statistically significant difference in the number of bond failures between the two methods. CLINICAL SIGNIFICANCE: The modified application phase of direct orthodontic bracket placement shortens the total bonding time and facilitates the manual work of orthodontists.

A Synopsis on CO2 Capture by Synthetic Hydrogen Bonding Receptors.

Carbon dioxide (CO2) is one of the most abundant greenhouse gases in Earth's atmosphere and responsible for global warming. Therefore, aerial CO2 capture and sequestration has become a major task for human community. Though several adsorbents for CO2 including activated carbon, zeolites, metal-organic frameworks (MOFs), and other surface-modified porous materials are well developed, the supramolecular approaches using synthetic hydrogen-bonding receptors are less explored. This review article highlights the synthetic development of various artificial receptors and their properties toward fixation of aerial CO2 as carbonate (CO32-), bicarbonate (HCO3-), or carbamate (-NHCOO-/>NCOO-) ions, induced by excess fluoride (F-) or hydroxide (OH-) ions as their tetrabutylammonium salts. The utilization of encapsulated carbonate/bicarbonate/carbamate complexes in anion exchange metathesis for separation of oxyanions from aqueous solutions are also discussed. In addition, the release of CO2 and regeneration of receptor molecules are described in a number of occasions. Most importantly, the formation of anion complexes as crystalline materials in solid-state is described in terms of supramolecular chemistry and correlated with their solution-state properties. Finally, the types of receptors containing various functional groups are scrutinized in CO2 uptake, storage, and release processes and hints of endeavours for future research are delineated.

Push-Out Bond Strength of Fiber Posts to Overflared Root Canals in Different Root Regions: Effect of Reinforcement Techniques.

Objectives: This study aimed to investigate the effect of different reinforcement techniques on the push-out bond strength of fiber posts to over-flared root canals. Materials and Methods: Forty-eight extracted human single-canal premolars were endodontically treated, over-flared, and randomly divided into four groups (N=12) including SARC: luting with self-adhesive resin cement, DCC: luting with dual-cure core build-up resin composite, CRR: relining root canal walls with bulk-fill resin composite, and DAP: relining fiber post with bulk-fill resin composite. After 24 hours, the roots were sectioned to obtain three cervical, middle, and apical 3mm slices. The push-out test was performed and failure pattern was examined. Kruskal-Wallis and post-hoc Dunn-Bonferroni tests were used for statistical analysis (P<0.05). Results: In all three regions, the lowest and highest bond strength was found in the SARC and DAP groups, respectively. In the middle region, there was a statistically significant difference between the bond strength of the SARC group and that of the DCC (P=0.044), CRR (P=0.021), and DAP (P<0.001) groups. There was no significant difference in the apical region. The lowest bond strength was observed in the apical region, and the highest was related to the cervical region. Adhesive failure was the most common failure pattern in all groups. Conclusion: Based on our results DCC, CRR and DAP methods increased bond strength in the middle and cervical sections of over-flared root regions. Considering that DCC is the easiest and most practical method, we propose that CRR and DAP can be replaced with this method in clinical procedures.

Enamel Deproteinization or Sandblasting for Enamel Reconditioning Before Acid Etching to Enhance the Shear Bond Strength of Metallic Brackets in a Third Bonding: An In Vitro Study.

BACKGROUND: Enamel conditioning with 37% phosphoric acid is the most common technique during orthodontic bracket bonding procedures. However, due to the repeated de-bonding of the orthodontic brackets during treatment, other methods were needed to condition the enamel surface and increase the bond strength. This study aimed to compare the effect of conditioning the enamel surface by sandblasting with aluminum oxide particles or 5.25% sodium hypochlorite gel in combination with acid etching compared to acid etching alone on shear bond strength (SBS). MATERIAL AND METHODS: One hundred eight extracted upper premolars were randomly divided into three groups according to the conditioning enamel surface method. After the first and second bonding of metal brackets, new metal brackets were bonded with a total-etching adhesive after enamel conditioning using different methods: acid etching only (37% phosphoric acid for 30 seconds) (AE group), sodium hypochlorite associated with acid etching (5.25% NaOCl gel for 60 seconds and then acid etching for 30 seconds) (NaOCl-AE group), and sandblasting associated with acid etching (sandblasting for five seconds and then acid etching for 30 seconds) (SB-AE group). The shear bond strengths of the brackets were tested with a universal testing machine. One-way analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) tests were used to detect significant differences in shear bond strength among groups at the third bonding. Repeated-measure ANOVA and Bonferroni's tests were used to detect significant differences in shear bond strength among the bonding attempts within each group. RESULTS: 5.25% sodium hypochlorite associated with the acid etching method produced significantly greater shear bond strength than sandblasting associated with acid etching and acid etching only methods at the third bonding (16.40 ± 5.80 MPa, 13.60.47 ± 6.40 MPa, and 9.90 ± 4.40 MPa, respectively; P < 0.001). However, there was no significant difference between the AE and SB-AE groups (P = 0.247). In addition, we found a significant decrease in the shear bond strength within each group after each bonding attempt. CONCLUSION: Conditioning the enamel surface with 5.25% sodium hypochlorite associated with acid etching produced greater bond strength than conditioning by sandblasting associated with acid etching and acid etching only at the third bonding. The bond strength of the metal bracket decreased with increasing bonding attempts, even with the application of enamel surface conditioning methods.

The Experience of Phenylketonuria in Pregnancy and the Developing Maternal-Infant Relationship: A Qualitative Study.

Phenylketonuria (PKU) is a rare metabolic condition characterised by an inability to metabolise phenylalanine (Phe), found in many foods. When pregnant with PKU, women must adhere to a strict low-Phe diet. If they do not, foetal abnormalities or pregnancy loss can occur. Pregnancies are therefore closely clinically monitored and dominated by dietary management, leaving little "space" for women's emotional experience. This article explores the emotional impact of PKU during pregnancy and how this effects pre-natal bonding. Based on interviews with six women with PKU, conducted whilst they were pregnant, this article explores their unusual and previously undocumented experience. Image-making during interviews allowed women to uncover aspects of their experience that might otherwise have remained hidden. Interpretative phenomenological analysis of the transcripts and images generated five themes summarising the women's experiences. Some themes reiterated findings from previous studies, for example, the huge cognitive burden associated with PKU pregnancies and the importance of both expert and informal support to successful pregnancy management. However, new understanding also emerged, including rich description of the emotional load of these pregnancies and strategies that women use to manage this. Anxiety about baby safety was central to their experiences, and the effect of this on pre-natal bonding was explored. This article calls for increased formal and informal support for women with the emotional aspects of their PKU pregnancies, for example, the creation of "attachment-aware" services that support women with their anxiety, promoting strong pre-natal attachment and subsequently protecting maternal and infant mental health throughout pregnancy and beyond.

Crystal structure of Staudtienic acid, a diterpenoid from Staudtia kamerunensis Warb. (Myristicaceae).

This title compound, C20H26O2, was isolated from the benzene fraction of the stem bark of Staudtia kamerunensis Warb. (Myristicaceae) using column chromatography techniques over silica gel. The compound was fully characterized by single-crystal X-ray diffraction, one and two-dimensional NMR spectroscopy, IR and MS spectrometry. The compound has two fused cyclo-hexane rings attached to a benzene ring, with a carb-oxy-lic acid on C-4. This cyclo-hexene ring has a chair conformation while the other adopts a half-chair conformation. The benzene ring is substituted with a propenyl moiety. The structure is characterized by inter-molecular O-H⋯O hydrogen bonds, two C-H⋯O intra-molecular hydrogen bonds and two C-H⋯π inter-actions. The mol-ecular structure confirms previous studies carried out by spectroscopic techniques.

Crystal structure of polymeric bis-(3-amino-1H-pyrazole)-cadmium diiodide.

The reaction of cadmium iodide with 3-amino-pyrazole (3-apz) in ethano-lic solution leads to tautomerization of the ligand and the formation of crystals of the title compound, catena-poly[[di-iodido-cadmium(II)]-bis-(µ-3-amino-1H-pyrazole)-κ2 N 2:N 3;κ2 N 3:N 2], [CdI2(C3H5N3)2] n or [CdI2(3-apz)2] n . Its asymmetric unit consists of a half of a Cd2+ cation, an iodide anion and a 3-apz mol-ecule. The Cd2+ cations are coordinated by two iodide anions and two 3-apz ligands, generating trans-CdN4I2 octa-hedra, which are linked into chains by pairs of the bridging ligands. In the crystal, the ligand mol-ecules and iodide anions of neighboring chains are linked through inter-chain hydrogen bonds into a di-periodic network. The inter-molecular contacts were qu-anti-fied using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing the relative qu-anti-tative contributions of the weak inter-molecular contacts.

Crystal structure determination and Hirshfeld surface analysis of N-acetyl-N-3-meth-oxy-phenyl and N-(2,5-di-meth-oxy-phen-yl)-N-phenyl-sulfonyl derivatives of N-[1-(phenyl-sulfon-yl)-1H-indol-2-yl]methanamine.

Two new [1-(phenyl-sulfon-yl)-1H-indol-2-yl]methanamine derivatives, namely, N-(3-meth-oxy-phen-yl)-N-{[1-(phenyl-sulfon-yl)-1H-indol-2-yl]meth-yl}acetamide, C24H22N2O4S, (I), and N-(2,5-di-meth-oxy-phen-yl)-N-{[1-(phenyl-sulfon-yl)-1H-indol-2-yl]meth-yl}benzene-sulfonamide, C29H26N2O6S2, (II), reveal a nearly orthogonal orientation of their indole ring systems and sulfonyl-bound phenyl rings. The sulfonyl moieties adopt the anti-periplanar conformation. For both compounds, the crystal packing is dominated by C-H⋯O bonding [C⋯O = 3.312 (4)-3.788 (8) Å], with the structure of II exhibiting a larger number, but weaker bonds of this type. Slipped π-π inter-actions of anti-parallel indole systems are specific for I, whereas the structure of II delivers two kinds of C-H⋯π inter-actions at both axial sides of the indole moiety. These findings agree with the results of Hirshfeld surface analysis. The primary contributions to the surface areas are associated with the contacts involving H atoms. Although II manifests a larger fraction of the O⋯H/H⋯O contacts (25.8 versus 22.4%), most of them are relatively distal and agree with the corresponding van der Waals separations.

Crystal structure of catena-poly[[methanoldioxidouranium(VI)]-µ-2-[5-(2-oxidophen-yl)-1H-1,2,4-triazol-3-yl]acetato-κ2 O:O'].

In the title complex, [U(C10H7N3O3)O2(CH3OH)] n , the UVI cation has a typical penta-gonal-bipyramidal environment with the equatorial plane defined by one N and two O atoms of one doubly deprotonated 2-[5-(2-hy-droxy-phen-yl)-1H-1,2,4-triazol-3-yl]acetic acid ligand, a carboxyl-ate O atom of the symmetry-related ligand and the O atom of the methanol mol-ecule [U-N/Oeq 2.256 (4)-2.504 (5) Å]. The axial positions are occupied by two oxide O atoms. The equatorial atoms are almost coplanar, with the largest deviation from the mean plane being 0.121 Šfor one of the O atoms. The benzene and triazole rings of the tetra-dentate chelating-bridging ligand are twisted by approximately 21.6 (2)° with respect to each other. The carboxyl-ate group of the ligand bridges two uranyl cations, forming a neutral zigzag chain reinforced by a strong O-H⋯O hydrogen bond. In the crystal, adjacent chains are linked into two-dimensional sheets parallel to the ac plane by C/N-H⋯N/O hydrogen bonding and π-π inter-actions. Further weak C-H⋯O contacts consolidate the three-dimensional supra-molecular architecture. In the solid state, the compound shows a broad medium intensity LMCT transition centred around 463 nm, which is responsible for its red colour.

Oxidative fluorination with Selectfluor: A convenient procedure for preparing hypervalent iodine(V) fluorides.

The ability to investigate hypervalent iodine(V) fluorides has been limited primarily by their difficult preparation traditionally using harsh fluorinating reagents such as trifluoromethyl hypofluorite and bromine trifluoride. Here, we report a mild and efficient route using Selectfluor to deliver hypervalent iodine(V) fluorides in good isolated yields (72-90%). Stability studies revealed that bicyclic difluoro(aryl)-λ5-iodane 6 was much more stable in acetonitrile-d 3 than in chloroform-d 1, presumably due to acetonitrile coordinating to the iodine(V) centre and stabilising it via halogen bonding.

Clinical Efficacy of a Novel Titania Nanoparticle-Reinforced Bonding Agent in Reducing Post-Restorative Sensitivity: A randomized clinical trial.

Objective: To evaluate the clinical efficacy of novel titania-nanoparticle reinforced bonding agent on post-restorative sensitivity in patients. Methods: This triple-blinded, randomized clinical trial included participants (n = 60) having Class- I and II cavitations with a minimum cavity depth of 3mm at Department of Operative Dentistry & Endodontics, School of Dentistry, Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad from January 5, 2023, to June 20, 2023. They were randomly assigned into two groups A and B (n = 30). After informed consent, restorative intervention was accomplished using an etch-and-rinse adhesive strategy. In Group-A, titania-nanoparticle-incorporated bonding agent was used for composite restoration, while in Group-B, bonding agent without nanoparticles was used. The primary outcome was assessed using Visual Analogue Scale mean score. Participants were instructed to rate their sensitivity status at follow-ups: 24 hours, one week, and one month. Mann-Whitney U test was employed to compare sensitivity between the two groups. Results: According to results of this trial, a significant difference was observed between two groups after 24 hours (p = 0.004) and one week (p = 0.002). However, no discernible difference was observed after one month (p = 0.643). Conclusion: Post-restorative sensitivity in patients with composite restorations was reduced using titania-reinforced bonding agents as compared to bonding agents without nanoparticles. This shows that inclusion of titania nanoparticles into adhesive dentistry could be beneficial in resolving post-restorative sensitivity occurring with composite restorations.

Bio-Inspired Carbon Dots as Malondialdehyde Indicator for Real-Time Visualization of Lipid Peroxidation in Depression.

Brain lipidic peroxidation is closely associated with the pathophysiology of various psychiatric diseases including depression. Malondialdehyde (MDA), a reactive aldehyde produced in lipid region, serves as a crucial biomarker for lipid peroxidation. However, techniques enabling real-time detection of MDA are still lacking due to the inherent trade-off between recognition dynamics and robustness. Inspired by the structure of phospholipid bilayers, amphiphilic carbon dots named as CG-CDs targeted to cell membrane are designed for real-time monitoring of MDA fluctuations. The design principle relies on the synergy of dynamic hydrogen bonding recognition and cell membrane targetability. The latter facilitates the insertion of CG-CDs into lipid regions and provides a hydrophobic environment to stabilize the labile hydrogen bonding between CG-CDs and MDA. As a result, recognition robustness and dynamics are simultaneously achieved for CG-CDs/MDA, allowing for in situ visualization of MDA kinetics in cell membrane due to the instant response (<5 s), high sensitivity (9-fold fluorescence enhancement), intrinsic reversibility (fluorescence on/off), and superior selectivity. Subsequently, CG-CDs are explored to visualize nerve cell membrane impairment in depression models of living cells and zebrafish, unveiling the extensive heterogeneity of the lipid peroxidation process and indicating a positive correlation between MDA levels and depression.

Molecular Design of Hole Transport Materials to Immobilize Ion Motion for Photostable Perovskite Solar Cells.

Poor operational stability is a crucial factor limiting the further application of perovskite solar cells (PSCs). Organic semiconductor layers can be a powerful means for reinforcing interfaces and inhibiting ion migration. Herein, two hole-transporting molecules, pDPA-SFX and mDPA-SFX, are synthesized with tuned substituent connection sites. The meta-substituted mDPA-SFX results in a larger dipole moment, more ordered packing, and better charge mobility than pDPA-SFX, accompany with strong interface bonding on perovskite surfaces and suppressed ion motion as well. Importantly, mDPA-SFX-based PSCs exhibit an efficiency that has significantly increased from 22.5% to 24.8% and a module-based efficiency of 19.26% with an active area of 12.95 cm2. The corresponding cell retain 94.8% of its initial efficiency at maximum power point tracking (MPPT) after 1,000 h (T95 = 1,000 h). The MPPT T80 lifetime is as long as 2,238 h. This work illustrates that a small degree of structural variation in organic compounds leaves considerable room for developing new HTMs for light stable PSCs.

Benefits of an online group dance program for adolescents' social bonding and wellbeing.

INTRODUCTION: The Covid-19 pandemic and its ensuing effects on mental health made it clearer than ever that social bonds are critical for survival, flourishing, and mental wellbeing. Experimental laboratory-based research with children and adults shows that activities involving movement alignment and joint action, such as dance, can facilitate social bonds. METHODS: This study examined whether an online group dance intervention positively affects social bonding and wellbeing using a randomized control design. Participants were 58 UK adolescents aged 11-16 years (N = 52 girls, 75% White, 7% Asian/Asian British, 18% Mixed-Other), randomly assigned to an online intervention or waitlist control group. Participants in the intervention group completed an online 5-week hip-hop dance program during the Covid-19 pandemic in January to February 2021. Measures of social bonding, wellbeing, and future orientation were taken at the beginning and end of the program. RESULTS: Linear mixed model analyses examining group × timepoint interaction showed greater increase in social bonding (p < .0001), and wellbeing (p < .0001) in the intervention vs control group. Moreover, increases in bonding significantly predicted increases in wellbeing (p < .0001), and increases in bonding (p = .03) and wellbeing (p = .0002) significantly predicted increases in the adolescents' hope for the future. CONCLUSIONS: These data, collected at a time of mass social isolation, show that a 5-week-long online dance activity can help adolescents forge stronger social bonds, and improve their wellbeing and future orientation. Our findings suggest that the wellbeing and future orientation benefits of group dance may stem from having stronger social connectedness, opening up avenues for future research and interventions.

Halogen-Functionalized Hole Transport Materials with Strong Passivation Effects for Stable and Highly Efficient Quasi-2D Perovskite Solar Cells.

The performance of quasi-two-dimensional (Q-2D) perovskite solar cells (PSCs) strongly depends on the interface characteristics between the hole transport material (HTM) and the perovskite layer. In this work, we designed and synthesized a series of HTMs with triphenylamine-carbazole as the core structure and modified end groups with chlorine and bromine atoms. These HTMs show deeper highest occupied molecular orbital energy levels than commercial HTMs. This reduced energy band mismatch between the HTM and perovskite layer facilitates efficient charge extraction at the interface. Moreover, these HTMs containing halogen atoms on the end groups could form halogen bonding with the Pb2+ ions at the buried interface of the perovskite layer, effectively passivating defects to suppress nonradiative recombination. Additionally, halogen bonding also contributes to the formation of vertically oriented perovskite crystals with a high quality. By incorporation of chlorohexane-substituted HTMs, the resultant Q-2D PSCs exhibited the highest power conversion efficiency of 21.07%. Furthermore, the devices show improved stability, retaining 97.2% of their initial efficiency after 1100 h of continuous illumination.

Trait mindfulness during pregnancy and maternal-infant bonding: Longitudinal associations with infant temperament and social-emotional development.

Maternal love and caregiving are pillars for optimal child development and may affect infant outcomes from pregnancy onwards. The present study aimed to examine whether maternal trait mindfulness during pregnancy and pre- and postnatal maternal-infant bonding were associated with maternal perceptions of infant temperament and social-emotional development. In total, 408 Dutch women (Mage = 31.33, SD = 3.59) participated in a prospective perinatal cohort study and completed questionnaires on trait mindfulness, prenatal bonding, postnatal bonding, infant temperament, and infant social-emotional development at 20 and 28 weeks of gestation, and 10 weeks, 6 and 12 months postpartum, respectively. Path analyses demonstrated that higher levels of the trait mindfulness facet non-judging (i.e., refraining from judgments about own feelings and thoughts) were associated with more pre- and postnatal maternal bonding and fewer social-emotional problems as perceived by the mother. Adopting an accepting and non-judgmental attitude may promote positive feelings of bonding and benefit the infant in terms of having fewer social-emotional problems in the first year of life. Mindfulness interventions may be offered to pregnant women in order to enhance maternal bonding and improve infant outcomes after birth.

Structure and intermolecular interactions in ionic liquid 1-ethyl-3-methylimidazolium bromide and its aqueous solutions investigated by vibrational spectroscopy and quantum chemical computations.

The recently developed efficient protocol to explicit quantum mechanical modeling of structure and IR spectra of liquids and solutions (S. A. Katsyuba, S. Spicher, T. P. Gerasimova, S. Grimme, J. Phys. Chem. B 2020, 124, 6664) is applied to ionic liquid (IL) 1-ethyl-3-methylimidazolium bromide (EmimBr), its C2-deuterated analog [Emim-d]Br and its aqueous solutions. It is shown that the solvation strongly modifies frequencies and IR intensities of the CH/CD stretching vibrations (νCH/νCD) of the imidazolium ring. The main vibrational spectroscopic features of the neat IL are reproduced by the simulations for a cluster (EmimBr)9, in which all three imidazolium CH moieties of the solvated cation form short contacts with three Br- anions, and another two Br- anions are located on top and bottom of imidazolium ring. Cluster models of aqueous solutions reproduce the experimental vibrational frequencies of actual solutions, provided that the Br- anion of solvated contact ion pair (CIP) is situated on top of imidazolium ring, and CH/CD moieties of the latter participate in short contacts with surrounding water molecules. Both structural and spectroscopic analysis allow to interpret the short contacts CH/CD⋯Br- and CH/CD⋯OH2 as hydrogen bonds of approximately equal strength. Enthalpies of bonding of these liquid-state H-bonds, estimated with the use of empirical correlations, amount to ca. 1.4 kcal⋅mol-1, while the analogous estimates obtained for the gas-phase charged species [Emim]2Br+ increase to 5.6 kcal⋅mol-1. It is shown that formation of solvent-shared ion pair (SIP) in aqueous solution, where the counterions of IL are separated by two water molecules H-bonded to a Br- anion, produces frequency shifts ΔνCH/CD, strongly different from the case of CIP formation. This difference can be used for IR/Raman spectroscopic differentiation of the type of solvated ion pairs of EmimBr or other related ILs.

Occupational modulation in the (3+1)-dimensional incommensurate structure of (2S,3S)-2-amino-3-hydroxy-3-methyl-4-phenoxybutanoic acid dihydrate.

The incommensurately modulated structure of (2S,3S)-2-amino-3-hydroxy-3-methyl-4-phenoxybutanoic acid dihydrate (C11H15NO4·2H2O or I·2H2O) is described in the (3+1)-dimensional superspace group P212121(0ß0)000 (ß = 0.357). The loss of the three-dimensional periodicity is ascribed to the occupational modulation of one positionally disordered solvent water molecule, where the two positions are related by a small translation [ca 0.666 (9) Å] and ∼168 (5)° rotation about one of its O-H bonds, with an average 0.624 (3):0.376 (3) occupancy ratio. The occupational modulation of this molecule arises due to the competition between the different hydrogen-bonding motifs associated with each position. The structure can be very well refined in the average approximation (all satellite reflections disregarded) in the space group P212121, with the water molecule refined as disordered over two positions in a 0.625 (16):0.375 (16) ratio. The refinement in the commensurate threefold supercell approximation in the space group P1121 is also of high quality, with the six corresponding water molecules exhibiting three different occupancy ratios averaging 0.635:0.365.