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The gas-phase molecular structure of iso-propyl(tert-butyl)(trichlorosilyl)phosphine has been determined using a combination of gas electron diffraction and computational methods. The structure presents a conformational challenge that required use of the SARACEN method to combine theoretical observations into the least-squares refinement process, a great advance on the techniques used to solve the structure of the parent trisilyl phosphine. Five conformers were found on the potential-energy surface for iso-propyl(tert-butyl)(trichlorosilyl)phosphine using the UCONGA program, and following a series of individual structure refinements a combined model with the two most abundant confirmers was evaluated. Key structural parameters (ra) include rP–Si [225.5(6) pm], rSi–Clmean [204.0(1) pm] and rP–Cmean [204.0(1) pm], ∠P–C–H 101.5(5)°, ∠C–C–C (iPr) 110.5(5)°, ∠C–C–C (tBu) 109.2(5)° and ∠C–P–C 105.4(5)°.

Background: We explored health professionals' views about the training, support, and resourcing needed to support people using closed-loop technology in routine clinical care to help inform the development of formal guidance. Methods: Interviews were conducted with health professionals (n = 22) delivering the Closed Loop from Onset in Type 1 Diabetes (CLOuD) trial after they had ≥6 months' experience of supporting participants using a closed-loop system. Data were analyzed descriptively. Results: Interviewees described how, compared with other insulin regimens, teaching and supporting individuals to use a closed-loop system could be initially more time-consuming. However, they also noted that after an initial adjustment period, users had less need for initiating contact with the clinical team compared with people using pumps or multiple daily injections. Interviewees highlighted how a lessened need for ad hoc clinical input could result in new challenges; specifically, they had fewer opportunities to reinforce users' diabetes knowledge and skills and detect potential psychosocial problems. They also observed heightened anxiety among some parents due to the constant availability of data and unrealistic expectations about the system's capabilities. Interviewees noted that all local diabetes teams should be empowered to deliver closed-loop system care, but stressed that health professionals supporting closed-loop users in routine care will need comprehensive technology training and standardized clinical guidance. Conclusion: These findings constitute an important starting point for the development of formal guidance to support the rollout of closed-loop technology. Our recommendations, if actioned, will help limit the potential additional burden of introducing closed-loop systems in routine clinical care and help inform appropriate user education and support.

The gas-phase molecular structure of iso-propyl(

Background:Closed-loop technology may help address health disparities experienced by adolescents, who are more likely to have suboptimal glycemic control than other age groups and, because of their age, find diabetes self-management particularly challenging. The CamAPS FX closed-loop has sought to address accessibility and usability issues reported by users of previous prototype systems. It comprises small components and a smartphone app used to: announce meal-time boluses, adjust (“boost” or “ease-off”) closed-loop insulin delivery, customize alarms, and review/share data. We explored how using the CamAPS FX platform influences adolescents’ self-management practices and everyday lives.Methods:Eighteen adolescents were interviewed after having ≥6 months experience using the closed-loop platform. Data were analyzed thematically.Results:Participants reported feeling less burdened and shackled by diabetes because closed-loop components were easier to carry/wear, finger-pricks were not required, the smartphone app provided a discreet and less stigmatizing way of managing diabetes in public, and they were able to customize alarms. Participants also reported checking and reviewing data more regularly, because they did so when using the smartphone for other reasons. Some reported challenges in school settings where use of personal phones was restricted. Participants highlighted how self-management practices were improved because they could easily review glucose data and adjust closed-loop insulin delivery using the “boost” and “ease-off” functions. Some described how using the system resulted in them forgetting about diabetes and neglecting certain tasks.Conclusions:A closed-loop system with small components and control algorithm on a smartphone app can enhance usability and acceptability for adolescents and may help address the health-related disparities experienced by this age group. However, challenges can arise from using a medical app on a device which doubles as a smartphone.Trial registration:Closed Loop From Onset in Type 1 Diabetes (CLOuD); NCT02871089; https://clinicaltrials.gov/ct2/show/NCT02871089

Aims To synthesise the qualitative evidence on parents’ experiences of caring for a child aged ≤8 years with type 1 diabetes to identify: the challenges they encounter; their views about support received; ways in which support could be improved; and, directions for future research. Methods We searched Medline, EMBASE, CINAHL, PsycINFO and Web of Science databases to identify qualitative studies reporting parents’ views and experiences of caring for a child with type 1 diabetes aged ≤8 years. Key analytical themes were identified using thematic synthesis. Results Fourteen studies were included. The synthesis resulted in the generation of two overarching themes. Monopolisation of life describes the all-encompassing impact diabetes could have on parents due to the constant worry they experienced and the perceived need for vigilance. It describes how parents’ caring responsibilities could affect their wellbeing, relationships and finances, and how a lack of trusted sources of childcare and a desire to enable a ‘normal’ childhood constrained personal choices and activities. However, use of diabetes technologies could lessen some of these burdens. Experiences of professional and informal support describes how encounters with healthcare professionals, while generally perceived as helpful, could lead to frustration and anxiety, and how connecting with other parents caring for a child with type 1 diabetes provided valued emotional and practical support. Conclusions This synthesis outlines the challenges parents encounter, their views about support received and ways in which support might be improved. It also highlights significant limitations in the current literature and points to important areas for future research, including how sociodemographic factors and use of newer diabetes technologies influence parents’ diabetes management practices and experiences. PROSPERO: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42019128710

Background: We explored parents’ experiences of using a hybrid closed-loop system when caring for a very young child with type 1 diabetes. Our objectives were to understand the impact of using this technology on users’ quality of life and inform its use in routine clinical care. Methods: Interviews were conducted with parents of 30 children (aged 1-7 years) who participated in a randomised controlled trial comparing closed-loop insulin delivery with sensor-augmented pump therapy. Findings: Parents reported major clinical benefits to using the closed-loop system, including more time being spent in range. Parents welcomed opportunities to collaborate with the system (using Ease-off and Boost functions) when their own knowledge could enhance its efficacy. Parents also reported a lessened need for health professional input after the initial transition onto the system had been made. Parents described wide-ranging quality-of-life benefits to using a system that automatically regulated blood glucose. Parents reported sleeping better, worrying less about their child and feeling more confident entrusting their child’s care to others, and how these individuals were more willing to assume caregiving responsibilities. Parents also described how their child felt more normal and experienced better sleep, mood and concentration, and lessened distress. Siblings also benefitted from parents’ time and attention being less focused on diabetes management. While parents highlighted multiple benefits to being able to administer insulin using a smartphone, difficulties were experienced stowing this device on the child’s body. Interpretation: Using a hybrid closed-loop system in very young children can have potentially life-changing consequences and may result in a lessened demand for health professionals’ input. Systems may need to be customised for use in very young children. Funding Information: The European Commission within the Horizon 2020 Framework Programme under the grant agreement number 731560 funded this work. Declaration of Interests: RH reports having received speaker honoraria from Eli Lilly and Novo Nordisk, serving on advisory panels for Eli Lilly and Novo Nordisk, receiving licence fees from BBraun and Medtronic. RH reports patent patents, patent applications, shareholding and directorship at CamDiab. FC has attended Advisory Boards and obtained speaking fees for Abbott, Medtronic, Lilly, and NovoNordisk. EFR reports having received speaker honoraria from Eli Lilly and Novo Nordisk, and serving on advisory boards for Eli Lilly and Sanofi. SH declares having received speakers honoraria from Eli Lilly, Sanofi and Pfizer. TMK has received speaking honoraria from Eli Lilly and MerckSerono, and consulted Sanofi for a transition brochure. BRM has received speaker honoraria from Abbott Diabetes Care, Eli Lilly, Medtronic, Novo Nordisk, Roche Diabetes Care, Sanofi and Menarini, and has been on the advisory boards of Roche Diabetes Care and Abbott Diabetes Care. The Authors JL, DR, RIH, CKB, JF, JMA, AT, US and BK declare that there is no conflict of interest. Ethics Approval Statement: Participants were consented into the interview study when they were consented into the trial. Approval was received from relevant Ethics Committees in participating sites/countries and relevant national regulatory authorities.

IntroductionThe successful treatment of type 1 diabetes (T1D) requires those affected to employ insulin therapy to maintain their blood glucose levels as close to normal to avoid complications in the long-term. The Dose Adjustment For Normal Eating (DAFNE) intervention is a group education course designed to help adults with T1D develop and sustain the complex self-management skills needed to adjust insulin in everyday life. It leads to improved glucose levels in the short term (manifest by falls in glycated haemoglobin, HbA1c), reduced rates of hypoglycaemia and sustained improvements in quality of life but overall glucose levels remain well above national targets. The DAFNEplus intervention is a development of DAFNE designed to incorporate behavioural change techniques, technology and longer-term structured support from healthcare professionals (HCPs).Methods and analysisA pragmatic cluster randomised controlled trial in adults with T1D, delivered in diabetes centres in National Health Service secondary care hospitals in the UK. Centres will be randomised on a 1:1 basis to standard DAFNE or DAFNEplus. Primary clinical outcome is the change in HbA1c and the primary endpoint is HbA1c at 12 months, in those entering the trial with HbA1c >7.5% (58 mmol/mol), and HbA1c at 6 months is the secondary endpoint. Sample size is 662 participants (approximately 47 per centre); 92% power to detect a 0.5% difference in the primary outcome of HbA1c between treatment groups. The trial also measures rates of hypoglycaemia, psychological outcomes, an economic evaluation and process evaluation.Ethics and disseminationEthics approval was granted by South West-Exeter Research Ethics Committee (REC ref: 18/SW/0100) on 14 May 2018. The results of the trial will be published in a National Institute for Health Research monograph and relevant high-impact journals.Trial registration numberISRCTN42908016.

AIM: To explore health professionals' views about who would benefit from using a closed-loop system and who should be prioritized for access to the technology in routine clinical care.METHODS: Health professionals (n = 22) delivering the Closed Loop from Onset in type 1 Diabetes (CLOuD) trial were interviewed after they had ≥6 months' experience supporting participants using a closed-loop system. Data were analysed thematically.RESULTS: Interviewees described holding strong assumptions about the types of people who would use the technology effectively prior to the trial. Interviewees described changing their views as a result of observing individuals engaging with the closed-loop system in ways they had not anticipated. This included educated, technologically competent individuals who over-interacted with the system in ways which could compromise glycaemic control. Other individuals, who health professionals assumed would struggle to understand and use the technology, were reported to have benefitted from it because they stood back and allowed the system to operate without interference. Interviewees concluded that individual, family and psychological attributes cannot be used as pre-selection criteria and, ideally, all individuals should be given the chance to try the technology. However, it was recognized that clinical guidelines will be needed to inform difficult decisions about treatment allocation (and withdrawal), with young children and infants being considered priority groups.CONCLUSIONS: To ensure fair and equitable access to closed-loop systems, prejudicial assumptions held by health professionals may need to be addressed. To support their decision-making, clinical guidelines need to be made available in a timely manner.

Few studies have identified determinants of glycemic control (HbA1c) and diabetes-specific quality of life (DSQoL) in adults with type 1 diabetes. To identify factors predicting outcomes following structured diabetes education. 262 participants completed biomedical and questionnaire assessments before, and throughout 1 year of follow-up. The proportion of variance explained ranged from 28 to 62 % (DSQoLS) and 14-20 % (HbA1c). When change in psychosocial variables were examined, reduced hypoglycemia fear, lower 'perceived diabetes seriousness', greater self-efficacy and well-being predicted QoL improvements from baseline to 3-months. Increased frequency of blood glucose testing predicted improvements in HbA1c from baseline to 6-months. Greater benefits may be achieved if programs focus explicitly on psychosocial factors. Self-care behaviours did not predict HbA1c suggesting existing assessment tools need refinement. Evaluation of treatment mechanisms in self-management programs is recommended.

BackgroundInsulin is generally administered to people with type 1 diabetes mellitus (T1DM) using multiple daily injections (MDIs), but can also be delivered using infusion pumps. In the UK, pumps are recommended for patients with the greatest need and adult use is less than in comparable countries. Previous trials have been small, of short duration and have failed to control for training in insulin adjustment.ObjectiveTo assess the clinical effectiveness and cost-effectiveness of pump therapy compared with MDI for adults with T1DM, with both groups receiving equivalent structured training in flexible insulin therapy.DesignPragmatic, multicentre, open-label, parallel-group cluster randomised controlled trial, including economic and psychosocial evaluations. After participants were assigned a group training course, courses were randomly allocated in pairs to either pump or MDI.SettingEight secondary care diabetes centres in the UK.ParticipantsAdults with T1DM for > 12 months, willing to undertake intensive insulin therapy, with no preference for pump or MDI, or a clinical indication for pumps.InterventionsPump or MDI structured training in flexible insulin therapy, followed up for 2 years. MDI participants used insulin analogues. Pump participants used a Medtronic Paradigm®VeoTM(Medtronic, Watford, UK) with insulin aspart (NovoRapid, Novo Nordisk, Gatwick, UK).Main outcome measuresPrimary outcome – change in glycated haemoglobin (HbA1c) at 2 years in participants whose baseline HbA1cwas ≥ 7.5% (58 mmol/mol). Key secondary outcome – proportion of participants with HbA1c≤ 7.5% at 2 years. Other outcomes at 6, 12 and 24 months – moderate and severe hypoglycaemia; insulin dose; body weight; proteinuria; diabetic ketoacidosis; quality of life (QoL); fear of hypoglycaemia; treatment satisfaction; emotional well-being; qualitative interviews with participants and staff (2 weeks), and participants (6 months); and ICERs in trial and modelled estimates of cost-effectiveness.ResultsWe randomised 46 courses comprising 317 participants: 267 attended a Dose Adjustment For Normal Eating course (132 pump; 135 MDI); 260 were included in the intention-to-treat analysis, of which 235 (119 pump; 116 MDI) had baseline HbA1cof ≥ 7.5%. HbA1cand severe hypoglycaemia improved in both groups. The drop in HbA1c% at 2 years was 0.85 on pump and 0.42 on MDI. The mean difference (MD) in HbA1cchange at 2 years, at which the baseline HbA1cwas ≥ 7.5%, was –0.24% [95% confidence interval (CI) –0.53% to 0.05%] in favour of the pump (p = 0.098). The per-protocol analysis showed a MD in change of –0.36% (95% CI –0.64% to –0.07%) favouring pumps (p = 0.015). Pumps were not cost-effective in the base case and all of the sensitivity analyses. The pump group had greater improvement in diabetes-specific QoL diet restrictions, daily hassle plus treatment satisfaction, statistically significant at 12 and 24 months and supported by qualitative interviews.LimitationBlinding of pump therapy was not possible, although an objective primary outcome was used.ConclusionAdding pump therapy to structured training in flexible insulin therapy did not significantly enhance glycaemic control or psychosocial outcomes in adults with T1DM.Research priorityTo understand why few patients achieve a HbA1cof Trial registrationCurrent Controlled Trials ISRCTN61215213.FundingThis project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full inHealth Technology Assessment; Vol. 21, No. 20. See the NIHR Journals Library website for further project information.

Summary Primula coelata Stapf is illustrated and a full description and typification are provided. Rediscovery of Primula bullata Franch. and P. bracteata Franch. in their type localities and analysis of herbarium specimens, living plants, historical documents and photographic data for the whole of Primula L. section Bullatae Pax have clarified the relationships between taxa. The whole section is revised. P. bracteata is restricted to plants conforming to Franchet's original concept, and becomes a variety of P. bullata, along with vars. bullata and forrestii. P. coelata is shown to be a valid name for one mat-forming species, the other one being P. rockii. P. henrici, with a cushion habit, has been reinstated as a distinct species.

The structures of the molecules C(SiXMe2)4 (X=H, F, Cl, Br) have been determined by gas electron diffraction (GED). Ab initio calculations revealed nine potential minima for each species, with significant ranges of energies. For the H, F, Cl, and Br derivatives nine, seven, two, and two conformers were modelled, respectively, as they were quantum-chemically predicted to be present in measurable quantities. Variable-temperature 1H and 29Si solution-phase NMR studies and, where applicable, 13C NMR, 1H/29Si NMR shift-correlation, and 1H NMR saturation-transfer experiments are reported for C(SiXMe2)4 (X=H, Cl, Br, and also I). At low temperature in solution two conformers (one C1-symmetric and one C2-symmetric) are observed for each of C(SiXMe2)4 (X=Cl, Br, I), in agreement with the isolated molecule ab initio calculations carried out as part of this work for X=Cl, Br. C(SiHMe2)4 is present as a single C1-symmetric conformer in solution at the temperatures at which the NMR experiments were performed.

Primula melanantha (Franch.) C. M. Hu, a taxon known from a single location in the south-west of Sichuan Province of China and with a long and confused taxonomic history, is described and illustrated. Its relationships with other members of subsection Maximowiczii of section Crystallophlomis are discussed, new keys are provided, and factors relevant to its successful cultivation are described.

Meconopsis wilsonii subsp. orientalis Grey-Wilson, Rankin & Wu, a new subspecies from north-east Yunnan Province of China, is described and illustrated. Its relationships with other members of subsection Eupolychaetia, particularly M. wallichii, M. violacea and the other subspecies of M. wilsonii, are discussed.

The molecular structures of 1-Br-4-F-C 6H 4 and 1-Cl-4-F-C 6H 4 have been studied in the gas phase using gas electron diffraction (GED) and ab initio methods. The structure of 1-Cl,4-F-C 6H 4 in the crystalline phase has also been studied, but whilst the gaseous structures were found to possess C 2v symmetry, the solid-state structure was found to be quite distorted, with three molecules in the asymmetric unit. These fragments only possess C s symmetry in the plane of the molecules, as opposed to the C 2v symmetry observed in the gas phase. The bonding motifs within the solid-state structure are very unusual and unexpected, with quite different C-F bond lengths for the three moieties, and are a result of weak hydrogen-halogen interactions within the structure. © 2010 Springer Science+Business Media, LLC.

The gas-phase structure of 1-adamantylphosphine has been determined by electron diffraction, supplemented with data from ab initio and DFT calculations. The adamantyl fragment was modeled with local C 3v symmetry and the phosphino group was found to be in a position almost bisecting a mirror plane of the adamantyl group, giving the molecule overall approximate C s symmetry. There is a small displacement of the C–P bond from the local threefold axis of the adamantyl group. Geometry optimizations were also performed for bis-(1-adamantyl)phosphine (C 1 point-group symmetry) and tris-(1-adamantyl)phosphine (C 3 symmetry), demonstrating extremely crowded environments around the phosphorus atoms leading to adamantyl groups that were much less symmetric. The adamantyl groups were also found to twist by a significant amount to minimize the strain.

The structure and conformations of 2-methylacetophenone (1) have been investigated by ab initio calculations carried out at the MP2(full)/6-311++G** level and by gas electron diffraction (GED). According to both methods, 1 exists predominantly as a form with the C=O bond synclinal with respect to the C(ar)-C(O) bond (1B), with a torsional angle [C(6)-C(1)-C=O] of 32.7(24) degrees as determined by GED and 26.0 degrees from MP2(full)/6-311++G**. Calculations also predict the presence of a second conformer, the anticlinal structure (1C), with phi = 140.0 degrees, with an abundance of less than 6%, an amount hardly detectable by GED. Different DFT computational protocols both support a nonplanar form of the predominant conformer (B2PLYP) and are in contradiction (B3LYP, M052x, B98, B97-D) with this experimental finding. The GED results, supported by the calculations that involve long-range correlation, are in a good agreement with (13)C NMR spectroscopic investigations, UV spectra, and dipole moment studies. However, previous claims that assumed steric inhibition of resonance caused by a significantly nonplanar conformation with phi close to 90 degrees have been disproved. Steric crowding is evident from the geometrical parameters, particularly from the C(1)-C(2) bond length and from the C(1)-C(2)-C(H(3)) and C(2)-C(1)-C(O) bond angles. It is concluded that any explanation of reactivity by steric inhibition of resonance and by other steric factors must be supported by experimental and/or theoretical investigation of the actual molecular shape.

Primula nghialoensis D. W. H. Rankin, a new species from Vietnam is described. It is assigned to the section Chartacea (Balf. f.) W.W.Sm., and its relationships with other members of this section, particularly P. petelotii, are discussed.

The molecular structure and conformational properties of ethyl trifluoroacetate, CF3CO2CH2CH3, were determined in the gas phase by electron diffraction, and vibrational spectroscopy (IR and Raman). The experimental investigations were supplemented by ab initio (MP2) and DFT quantum chemical calculations at different levels of theory. Experimental and theoretical methods result in two structures with Cs (anti–anti) and C1 (anti–gauche) symmetries, the former being slightly more stable than the latter. The electron-diffraction data are best fitted with a mixture of 56% anti–gauche and 44% anti–anti conformers. The conformational preference was also studied using the total energy scheme, and the natural bond orbital scheme. Also, the infrared spectra of CF3CO2CH2CH3 are reported for the gas, liquid and solid states, as is the Raman spectrum of the liquid. The comparison of experimental averaged IR spectra of Cs and C1 conformers provides evidence for the predicted conformations in the IR spectra. Harmonic vibrational wavenumbers and scaled force fields have been calculated for both conformers. Copyright © 2009 John Wiley & Sons, Ltd.

A conformational study of diethyldichlorosilane and the elucidation of the gas-phase molecular structures of its four conformers have been performed using the combined approach of gas-phase electron diffraction and computational techniques. Moreover, the Raman spectrum of the liquid and the IR spectra of the gas and liquid phases have been recorded and thoroughly analyzed on the basis of the scaled quantum-mechanical force field methodology. The results of the vibrational assignment have given spectroscopic evidence of the presence of the different conformers in the samples. Copyright c � 2009 John Wiley & Sons, Ltd.

The molecular structures of allyl-, allenyl-, propargyl-, vinyl-, ethynyl-, phenyl-, benzyl-, and chloromethyl-phosphine have been determined from gas-phase electron diffraction data employing the SARACEN method. The experimental geometric parameters are compared with those obtained using ab initio calculations performed at the MP2 level using both Pople-type basis sets and the correlation-consistent basis sets of Dunning. The structure and conformational behavior of each molecule have been analyzed and, where possible, comparisons made to the analogous amine. For systems with multiple conformers, differences in the CCP bond angle of approximately 5 degrees between conformers are common. Trends in the key parameters are identified and compared with those found in similar systems.

The molecular structure of methyl trifluoroacetate (CF3C(O)OCH3) has been determined in the gas phase from electron-diffraction data supplemented by ab initio (MP2) and DFT calculations using different basis sets. Experimental data revealed an anti conformation with a dihedral angle θ (CCOC) = 180°. Quantum mechanical calculations indicate the possible existence of two conformers, differing by a rotation about the C(O)O bond. The global minimum represents a Cs-symmetric structure in which the CF3 group has the anti orientation with respect to the CH3 group, but there is another potential minimum, much higher in energy, representing a Cs-symmetric structure with a cis conformation. The preference for the anti conformation was studied using the total energy scheme and the natural bond orbital (NBO) partition scheme. Additionally, the total potential energy has been deconvoluted using a six-fold decomposition in terms of a Fourier-type expansion, showing that the electrostatic and steric contributions are dominant in stabilizing the anti conformer. Infrared spectra of CF3C(O)OCH3 were obtained for the gaseous and liquid phases, while the Raman spectrum was recorded for the liquid phase. Harmonic vibrational frequencies and a scaled force field have been calculated, leading to a final root mean-square deviation of 9 cm−1 when comparing experimental and calculated frequencies. Copyright © 2009 John Wiley & Sons, Ltd.

The development of modern computational methods, linked to improved methods for analysis of experimental gas-phase structural data, has allowed the stereochemistry of many boranes and heteroboranes to be determined with great accuracy over the past two decades. Many of these compounds have been prepared in the Institute of Inorganic Chemistry of the Academy of Sciences of the Czech Republic, and gas-phase electron diffraction (GED) data have been obtained mainly at the University of Edinburgh. Structural tools based on the concerted use of GED and computations of the geometries and 11B chemical shifts (MOCED, SARACEN) have also been employed. The results of this extended programme of research are reviewed here. Many different closo-, nido-, arachno-, and hypho- geometrical shapes, as well as some that do not obey Wade's rules, are included. The outlook for the future of this type of structural chemistry research is assessed.

The accurate structures of silsesquioxanes Si8O12H8 and Si8O12Me8 have been determined by gas-phase electron diffraction methods in order to obtain experimental data on single molecules unconstrain...

The gas-phase structures of Al(But)3 and Ga(But)3 have been investigated by electron diffraction and are shown to consist of monomeric units with very slightly pyramidal geometries. Salient structural parameters (rh1) include r(Al-C) = 2.008(2) Å and r(Ga-C) = 2.032(2) Å. For both compounds the ligand orientations and geometries are controlled by interligand interactions. The structures of M(But)3 (M = Al, Ga, In) have been calculated ab initio and those for the aluminium and gallium derivatives are in good agreement with the electron-diffraction structures. Comparison of the ab initio calculated structure of In(But)3 with those of Al(But)3 and Ga(But)3 suggests that the significantly different photochemistry exhibited by the former does not result from structural factors. In fact the compounds undergo a charge-transfer process in the UV region, with the wavelength required calculated to be slightly longer for the indium compound than for the other two.

Molecular structures of dimethylbis(trimethylsilylketyl)silane (Me 2 Si[C(SiMe 3 ) C O] 2 ), dimethylbis(trimethylgermylketyl)silane (Me 2 Si[C(GeMe 3 ) C O] 2 ), and dimethylbis(trimethylstannylketyl)germane (Me 2 Ge[C(SnMe 3 ) C O] 2 ) have been studied in the gas phase by electron diffraction accompanied by high level ab initio and DFT calculations. Extensive theoretical conformational analyses of the molecules in the vapour predicted a possibility of existence of two types of conformers with small energy differences. The first type had gauche – gauche arrangements of the ketenyl groups in the central C( C O)XC( C O) fragments directed away from each other. The second type had nearly syn – gauche arrangements of the ketenyl groups. In addition, the energy differences were found to depend on the level of computations used. The experimental analysis, in turn, was unable to distinguish between different conformers due to the large number of similar overlapping distances. The experimental data were fitted by an averaged single-conformer model, which nevertheless allowed reliable determination of bonds and bonded angles in the molecules. Main experimental ( r h1 ) structural parameters for Me 2 Si[C(SiMe 3 ) C O] 2 , Me 2 Si[C(GeMe 3 ) C O] 2 , and Me 2 Ge[C(SnMe 3 ) C O] 2 , i.e. Me 2 X[C(YMe 3 ) C O] 2 (X,Y = Si, Ge, Sn), are (X–C) mean 187.7(1) pm, 194.6(2) pm, 216.1(3) pm; (Y–C) mean , 187.7(1) pm, 188.8(8) pm, 194.6(4) pm; (C C) mean , 135.3(5) pm, 131.6(5) pm, 131.5(13) pm; (C O) mean , 117.0(7) pm, 117.4(7) pm, 119.0(11) pm; (C–H) mean , 110.6(7) pm, 110.0(4) pm, 109.1(13) pm; (X(Y)–C C) mean , 114.4(2)°, 115.6(1)°, 115.6(2)°; (C–X(Y)–C Me ) mean , 108.3(3)°, 108.4(3)°, 108.9(13)°; C(2)–C(1)–Y(4)–C(10), −19(6)°, 5(4)°, −9(10)°; C(7)–C(6)–Y(9)–C(38),−22(7)°, −32(3)°, −9(10)°; C(2)–C(1)–X(5)–C(6), 128(4)°, 142(1)°, 108(9)°; C(7)–C(6)–X(5)–C(1), 92(6)°, 115(2)°, 108(9)°, respectively.

A new method of incorporating ab initio theoretical data dynamically into the gas-phase electron diffraction (GED) refinement process has been developed to aid the structure determination of large, sterically crowded molecules. This process involves calculating a set of differences between parameters that define the positions of peripheral atoms (usually hydrogen), as determined using molecular mechanics (MM), and those which use ab initio methods. The peripheral-atom positions are then updated continually during the GED refinement process, using MM, and the returned positions are modified using this set of differences to account for the differences between ab initio and MM methods, before being scaled back to the average parameters used to define them, as refined from experimental data. This allows the molecule to adopt a completely asymmetric structure if required, without being constrained by the MM parametrization, whereas the calculations can be performed on a practical time scale. The molecular structures of tri-tert-butylphosphine oxide and tri-tert-butylphosphine imide have been re-examined using this new technique, which we call SEMTEX (Structure Enhancement Methodology using Theory and EXperiment).

Conformational studies of triethylchlorosilane (TECS) and triethylbromosilane (TEBS) and the elucidation of their gas phase molecular structures have been accomplished by the combined use of theoretical (ab initio and density functional theory) calculations and experimental data from gas phase electron diffraction experiments. Additionally, analysis of the experimental features observed in the IR and Raman spectra recorded for both compounds has allowed us to propose a complete description of the vibrational spectra of both compounds, including an explanation of certain bands, which can only be correctly assigned when more than one conformer is considered to be present.

Trifluoromethyl trifluoromethanesulfonate, CF3SO2OCF3, has been synthesised and its gas-phase structure determined from electron-diffraction data. This structural study was supported by HF, MP2 and DFT (B3LYP and B1B95) calculations, which revealed a strong dependence of the theoretical structure on the polarisation of the basis set. Infrared spectra for the gas and solid and a Raman spectrum for the liquid were obtained, and the observed bands were assigned. The experimental vibrational data, along with theoretical (B3LYP) force constants, were used to define a scaled quantum mechanical force field, which enabled reproduction of the measured frequencies with a final root-mean-square deviation of 6 cm–1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The molecular structures of dimethylbis(trichlorosilyl)germane [Me 2 Ge(SiCl 3 ) 2 ] and trimethyl(trichlorosilyl)germane (Me 3 GeSiCl 3 ) have been determined in the gas phase. Me 3 GeSiCl 3 was found ab initio to possess C 3 v symmetry, with a low-lying torsional motion of the SiCl 3 group relative to the GeMe 3 group. The gas electron diffraction data were modelled with C 3 symmetry, although little deviation from C 3 v symmetry was observed. Me 2 Ge(SiCl 3 ) 2 ( C 2 v symmetry) was also found to have a very low-lying vibrational frequency relating to the rotation of the SiCl 3 groups. This led to the gas electron diffraction data being modelled in C 2 symmetry, with the observed combined deviation of the SiCl 3 groups being 14° from the eclipsed structure calculated ab initio. The Ge–C bond lengths were unaffected by the addition of an extra SiCl 3 group to the central germanium atom, but the Ge–Si bond lengths were observed to increase by over 1 pm.

The electrophilic addition reactions of methylsulfenyl chloride to the double bonds of functionalized ethenes have been studied theoretically. Density functional theory (DFT) calculations have been applied for starting species and ethene-based sulfonium intermediates bearing substitutes at α-carbon atom to study geometrical parameters and electronic states of plausible intermediate forms. The quantum chemical optimizations of intermediates indicate that the episulfonium ion is the most likely methyl- or carboxyl-substituted ethane-based intermediate. However, with phenyl substituents the intermediate is more like a carbonium than an episulfonium ion. The role of sulfur appears to be that of directing the stereochemistry of the addition reaction of chloride, forming the trans product upon nucleophilic attack on the C—C bond of the episulfonium ion. The regioselectivity features of the opening of the episulfonium ion by the chloride anion depend on the LUMO and LUMO+1 of the episulfonium ion and the approaching HOMO of chlorine. The results of the theoretical investigations are in agreement with experiment. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:695–703, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20378

The gas-phase structure of 6,9-CSB8H12 has been determined by electron diffraction and ab initio calculations, and that of 6,9-CNB8H13 has also been calculated. The accuracy of each structure has been confirmed by 11B NMR calculations. The position of the sulfur atom is very close to that of the boron atom occupying the equivalent position in the parent molecule [B10H14](2-), reflecting the similarity of sizes of sulfur and boron atoms. The nitrogen and carbon atoms, on the other hand, lie much closer to the centers of the cages. The B8-X9-B10 angles increase from 98.7 degrees for X = S to 122.8 degrees for X = N. There are also large changes in relative lengths of bonds, with some bonds lengthening by up to 14.6 pm on introduction of a sulfur atom.

Ti(NMe2)4 is a monomeric species in the gas phase and in solution, and this remains true on crystallisation. The crystal structure is triclinic, with space group P 1 ¯ , and unit cell dimensions a = 8.277(6), b = 8.407(6), c = 11.167(7) A, α = 105.36(4)°, β = 97.03(3)° and γ = 116.01(2)° at 105 K. Electron-diffraction measurements show that in the gas-phase Ti(NMe2)4 takes the form of a slightly flattened tetrahedron with overall S4 symmetry. In the solid state the symmetry changes to C1; the reduction of point-symmetry results from the twisting of one of the amino groups away from its gas-phase configuration. DFT calculations indicate that the energy of the C1 structure lies only 0.2 kJ mol−1 above that of the S4 conformer. The change in structure on crystallisation can be ascribed to the avoidance of prohibitively short intermolecular methyl–methyl interactions which would have been formed had the S4 structure been retained.

Combined gas electron diffraction/mass spectrometry (GED/MS) was used to determine the molecular structure of tris(hexafluoroacetylacetonato)scandium(III), Sc(hfa) 3 (hfa=1,1,1,5,5,5-hexafluoropentane-2,4-dionato). The experimental data recorded at 310(5) K indicate that the molecules have D 3 symmetry. The bond distances ( r h 1 ) in the chelate ring are Sc–O 2.084(5), C–O 1.268(8) and C–C 1.411(10) A. Theoretical computations at the HF and DFT levels with basis sets up to Ahlrich valence triple-ξ (VTZ) afford structures similar to those found experimentally, with a distorted ScO 6 antiprism.

The molecular structure and conformation of 1, 1, 1,4,4,4-hexachloro- 1,4-disilabutane in the gas-phase have been determined by electron diffraction and computational methods. The lowest-energy conformation has the trichlorosilyl groups anti to one another. The gauche conformation also has a shallow potential minimum, but lies about 19 kJ mol(-1) above the anti form. Calculations on related butane derivatives, in which terminal methyl groups have been replaced by CCl3, SiH3 and SiCl3 groups, reveal that the conformational preferences are primarily caused by steric interactions between the terminal groups, and that it is the presence of chlorine atoms that destabilises gauche conformations. The electronegativity of the chlorine atoms has only small effects, mainly limited to the Si-Cl bond lengths. (c) 2004 Elsevier B.V. All rights reserved.

The gas-phase molecular structures of 6,8-difluoro-1,3λ4δ2,2,4-benzodithiadiazine and 5,6,7-trifluoro-1,3λ4δ2,2,4-benzodithiadiazine have been determined using quantum chemical calculations and electron diffraction via the SARACEN method of structural analysis. Of particular interest was the planarity or nonplanarity of the heterocyclic fragments of the molecules. It was shown that the difluoro compound is planar with respect to the heterocyclic fragment [folding angle: 0.0(5)° (figures in parenthesis indicate e.s.d.s in the final digits)] and that the trifluoro compound probably deviates from planarity to a small extent [folding angle: 4.0(−30;+3)°; the large uncertainty in the value of this angle is due to the low-frequency, large-amplitude vibrational motion associated with the folding of the heterocyclic fragment]. Pertinent structural parameters from the electron diffraction data (rh1 structure) of the difluoro compound are av[r(S=N)] = 155.7(7) pm, r(S−N) = 175.8(5) pm, r(C−S) = 176.6(8) pm and r(C−N) = 141.6(2) pm. For the trifluoro compound the equivalent structural parameters are av[r(S=N)] = 155.5(7) pm, r(S−N) = 170.7(6) pm, r(C−S) = 180.6(8) pm and r(C−N) = 140.6(2) pm. The gas-phase electron diffraction structures have been compared with results from ab initio and DFT calculations and also with experimental solid-state structures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Nine organotin fluorocarboxylates R n SnO 2 CR f (n = 3, R = Bu, R f = CF 3 , C 2 F 5 , C 3 F 7 , C 7 F 15 ; R = Et, R f = CF 3 , C 2 F 5 ; R = Me, R f = C 2 F 5 ; n = 2, R = Me, R f = CF 3 ) have been synthesized; key examples have been used to deposit fluorine-doped SnO 2 thin films by atmospheric pressure chemical vapour deposition. Et 3 SnO 2 CC 2 F 5 , in particular, gives high-quality films with fast deposition rates despite adopting a polymeric, carboxylate-bridged structure in the solid state, as determined by X-ray crystallography. Gas-phase electron diffraction on the model compound Me 3 SnO 2 CC 2 F 5 shows that accessible conformations do not allow contact between tin and fluorine, and that direct transfer is therefore unlikely to be part of the mechanism for fluorine incorporation in SnO 2 films. The structure of Me 2 Sn(O 2 CCF 3 ) 2 (H 2 O) has also been determined and adopts a trans-Me 2 SnO 3 coordination sphere about tin in which each carboxylate group is monodentate.

The determination of structure in the gas phase is an important technique for obtaining accurate structural information for molecules, free from intermolecular interactions that could affect solid-state structures. For large asymmetric molecules, obtaining the full gas-phase structure using experimental data alone is virtually impossible in most cases. The utilisation of theoretical methods in the determination of the experimental molecular structure has allowed many more molecules to be studied, revealing important structural information. This information can be used by theoreticians to develop their methods further, and so both experimentalists and theoreticians benefit. This article describes the development of these methods and uses some examples to demonstrate their importance. These include the determination of the gaseous molecular structures of ferrocene and isopropylferrocene, and of the bis[bis(trimethylsilyl)methyl]phoshido radical, for which Density Functional Theory is realistically the only theoretical method available to aid the determination of the gas-phase structure. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005

O-(Dichlorosilyl)-N,N-dimethylhydroxylamine, Cl2HSiONMe2, was synthesised by the reaction of O-lithio-N,N-dimethylhydroxylamine with an excess of trichlorosilane. The compound was characterised by multinuclear NMR spectroscopy (1H, 13C, 15N, 29Si), gas-phase IR spectroscopy and mass spectrometry. The structure of Cl2HSiONMe2 was determined by gas-phase electron diffraction. It exists as two conformers in the vapour, named anti and gauche after the position of the SiH hydrogen atom relative to the SiON skeleton. The anti:gauche ratio in the vapour was determined to be 40:60. The anti conformer shows only a weak attractive interaction between the geminal donor and acceptor centres N and Si [angle Si-O-N 111.1(20)­°], whereas these interactions are stronger in the gauche conformer [angle Si-O-N 98.8(12)°]. Further structure-determining forces from weak hydrogen bridges of the Si-Cl ···H-C type and van der Waals repulsive forces are also discussed. The experimental results are in reasonable agreement with ab initio calculations at the MP2/6-311++G** level of theory.

From the whole plant of Senecio tsoongianus, two pairs of epimers, tsoongianolides A (1) and B (2), and tsoongianolides C (3) and D (4), and two new sesquiterpene lactones, tsoongianolides E (5) and F (6), all of which possess the eremophilane skeleton, were isolated. Two known eremophilane dimers (7) and (8) were also obtained from this species. Their absolute structures were elucidated by 1D- and 2D-NMR techniques and by X-ray diffraction studies, along with chemical evidence.

We have developed methodology for the determination of solution structures of small molecules from residual dipolar coupling constants measured in dilute liquid crystals. The power of the new technique is demonstrated by the determination of the structure of methyl β-d-xylopyranoside (I) in solution. An oriented sample of I was prepared using a mixture of C12E5 and hexanol in D2O. Thirty residual dipolar coupling constants, ranging from −6.44 to 4.99 Hz, were measured using intensity-based J-modulated NMR techniques. These include 15 DHH, 4 1DCH, and 11 nDCH coupling constants. The accuracy of the dipolar coupling constants is estimated to be

The molecular structures of two carbaboranes, closo-2,3-C(2)B(9)H(11) and nido-2,9-C(2)B(9)H(13), were determined experimentally for the first time using gas-phase electron diffraction (GED). For closo-2,3-C(2)B(9)H(11), a model with C(2)(v)() symmetry was refined to give C-B bond distances ranging 158.3-167.0 pm and B-B distances ranging 177.4-200.0 pm. The structure of nido-2,9-C(2)B(9)H(13) was refined using a model with C(s)() symmetry to give C-B bond lengths ranging 160.3-171.9 pm and B-B lengths ranging 173.0-196.1 pm. Ab initio computations (up to MP2/6-311+G) were also carried out on these and the related nido-7,8-C(2)B(9)H(13), which was not sufficiently stable to allow determination of its molecular structure by GED.

The molecular structures of the diphosphines P(2)[CH(SiH(3))(2)](4), P(2)[C(SiH(3))(3)](4), P(2)[SiH(CH(3))(2)](4), and P(2)[Si(CH(3))(3)](4) and the corresponding radicals P[CH(SiH(3))(2)](2), P[C(SiH(3))(3)](2), P[SiH(CH(3))(2)](2), and P[Si(CH(3))(3)](2) were predicted by theoretical quantum chemical calculations at the HF/3-21G*, B3LYP/3-21G*, and MP2/6-31+G* levels. The conformational analyses of all structures found the gauche conformers of the diphosphines with C(2) symmetry to be the most stable. The most stable conformers of the phosphido radicals were also found to possess C(2) symmetry. The structural changes upon dissociation allow the release of some of the energy stored in the substituents and therefore contribute to the decrease of the P-P bond dissociation energy. The P-P bond dissociation enthalpies at 298 K in the compounds studied were calculated to vary from -11.4 kJ mol(-1) (P(2)[C(SiH(3))(3)](4)) to 179.0 kJ mol(-1) (P(2)[SiH(CH(3))(2)](4)) at the B3LYP/3-21G* level. The MP2/6-31+G* calculations predict them to be in the range of 52.8-207.9 kJ mol(-1). All the values are corrected for basis set superposition error. The P-P bond energy defined by applying a mechanical analogy of the flexible substituents connected by a spring shows less variation, between 191.3 and 222.6 kJ mol(-1) at the B3LYP/3-21G level and between 225.6 and 290.4 kJ mol(-1) at the MP2/6-31+G* level. Its average value can be used to estimate bond dissociation energies from the energetics of structural relaxation.

The structure of the gallane adduct Me3P·GaH3 in the vapour and crystalline states has been investigated. The gas-phase electron-diffraction (GED) pattern has been analysed using the SARACEN method to determine the most reliable structure of the gaseous molecule. Salient structural parameters (rh1 structure) were found to be: r(Ga–H) 159.0(11), r(Ga–P) 244.3(6), r(P–C) 184.0(2), r(C–H) 108.3(7) pm; H–Ga–P 98.4(12) and Ga–P–C 117.7(3)°. The structure of a single crystal at 150 K shows that the adduct retains the same monomeric unit in the crystalline phase, with dimensions generally close to those of the gaseous molecule and an eclipsed conformation of the C3PGaH3 skeleton. The results are discussed and analysed in the light of quantum chemical calculations and of the properties of related adducts of Group 13 metal hydrides.

Gas-phase electron diffraction is a powerful technique for structural analysis of molecules in the gas phase, where they are free from packing forces that can occur in crystals. The compound B(BF2)3CO has been studied by gas-phase electron diffraction to compare its structure to that seen in the solid phase by low-temperature X-ray crystallography. Results show the gas-phase structure to be similar to that seen in the crystal. A model with C3 symmetry refined to give a C–O bond length of 115.8 pm and a C–B bond distance of 150.2 pm, which compare to values of 111.7 and 152.2 pm for the solid phase. The family of borane carbonyl compounds B(BX2)3CO (X = F, Cl, Br or I) have all been studied by ab initio calculations to show the effects of halogen substitution and to gauge the effects of electron correlation and basis set on each structure. Compounds X = F, Cl and Br give calculated structures with C3 symmetry in which the boron–halogen bonds lie coplanar with the C–O bond. In the case of X = I, the BI2 groups are twisted by approximately 35° from coplanar at the DFT level as a result of the large steric interactions between iodine atoms.

A molecular mechanics force field has been developed for the conformational analysis of amido- and α-aminoferrocenes. Parameterization for ring-substituent rotational barriers in amidoferrocenes and other cross-conjugated derivatives have been calculated using DFT on both the free and complexed cyclopentadienyl ligand. Modeled structures of (diisopropylamido)- and (dimethylamido)ferrocene and N,N-dimethyl-α-ferrocenylethylamine are in agreement with those determined through single-crystal X-ray diffraction. The diastereoselective lithiation of N,N-dimethylferrocenylethylamine and sparteine-mediated enantioselective lithiation of (diisopropylamido)ferrocene using MeLi have been modeled through an assumed reversible adduct formation at the amine nitrogen or amide oxygen, followed by an irreversible ring lithiation. Results indicate that selectivity results from ring lithiation via the adduct conformer with the shortest C−Hring- - -H3C−Li interaction.

The structure of Ru(C5Me5)(C5F5) has been determined by gas-phase electron diffraction and density functional theory. Comparison structures of the known compounds Ru(C5H5)2 and Ru(C5F5)(C5H5), as well as the unknown compound Ru(C5F5)2, have also been determined by density functional theory.

BackgroundMany adults with type 1 diabetes cannot self-manage their diabetes effectively and die prematurely with diabetic complications as a result of poor glucose control. Following the positive results obtained from a randomised controlled trial (RCT) by the Dose Adjustment For Normal Eating (DAFNE) group, published in 2002, structured training is recommended for all adults with type 1 diabetes in the UK.AimWith evidence that blood glucose control is not always improved or sustained, we sought to determine factors explaining why some patients benefit from training more than other patients, identifying barriers to successful self-management, while developing other models to make skills training more accessible and effective.FindingsWe confirmed that glycaemic outcomes are not always improved or sustained when the DAFNE programme is delivered routinely, although improvements in psychosocial outcomes are maintained. DAFNE courses and follow-up support is needed to help participants instil and habituate key self-management practices such as regular diary/record keeping. DAFNE graduates need structured professional support following training. This is currently either unavailable or provided ad hoc without a supporting evidence base. Demographic and psychosocial characteristics had minimal explanatory power in predicting glycaemic control but good explanatory power in predicting diabetes-specific quality of life over the following year. We developed a DAFNE course delivered for 1 day per week over 5 weeks. There were no major differences in outcomes between this and a standard 1-week DAFNE course; in both arms of a RCT, glycaemic control improved by less than in the original DAFNE trial. We piloted a course delivering both the DAFNE programme and pump training. The pilot demonstrated the feasibility of a full multicentre RCT and resulted in us obtaining subsequent Health Technology Assessment programme funding. In collaboration with the National Institute for Health Research (NIHR) Diabetes Research Programme at King’s College Hospital (RG-PG-0606-1142), London, an intervention for patients with hypoglycaemic problems, DAFNE HART (Dose Adjustment for Normal Eating Hypoglycaemia Awareness Restoration Training), improved impaired hypoglycaemia awareness and is worthy of a formal trial. The health economic work developed a new type 1 diabetes model and confirmed that the DAFNE programme is cost-effective compared with no structured education; indeed, it is cost-saving in the majority of our analyses despite limited glycated haemoglobin benefit. Users made important contributions but this could have been maximised by involving them with grant writing, delaying training until the group was established and funding users’ time off work to maximise attendance. Collecting routine clinical data to conduct continuing evaluated roll-out is possible but to do this effectively requires additional administrator support and/or routine electronic data capture.ConclusionsWe propose that, in future work, we should modify the current DAFNE curricula to incorporate emerging understanding of behaviour change principles to instil and habituate key self-management behaviours that include key DAFNE competencies. An assessment of numeracy, critical for insulin dose adjustment, may help to determine whether or not additional input/support is required both before and after training. Models of structured support involving professionals should be developed and evaluated, incorporating technological interventions to help overcome the barriers identified above and enable participants to build effective self-management behaviours into their everyday lives.Trial registrationClinicalTrials.gov NCT01069393.FundingThe NIHR Programme Grants for Applied Research programme.

Background Children with type 1 diabetes (T1D) experience poor glycaemic control. Among non-adolescent children, parents assume much responsibility for managing diabetes and attaining blood glucose levels within clinically recommended target ranges. We explored parents’ experiences of managing their child’s diabetes and reasons for treatment non-adherence in order to identify better ways to support them. Methods In-depth interviews with 54 parents of children with T1D (aged ≤ 12 years), recruited from four Scottish paediatric diabetes clinics. Data were …