Dr James Wright

A family of one-dimensional coordination polymers, [Ag4(O2C(CF2)2CF3)4(phenazine)2(arene)n]·m(arene), 1 (arene = toluene or xylene), have been synthesized and crystallographically characterized. Arene guest loss invokes structural transformations to yield a pair of polymorphic coordination polymers [Ag4(O2C(CF2)2CF3)4(phenazine)2], 2a and/or 2b, with one- and two-dimensional architectures, respectively. The role of pre-organization of the polymer chains of 1 in the selectivity for formation of either polymorph is explored, and the templating effect of toluene and p-xylene over o-xylene or m-xylene in the formation of arene-containing architecture 1 is also demonstrated. The formation of arene-free phase 2b, not accessible in a phase-pure form through other means, is shown to be the sole product of loss of toluene from 1-tol·tol [Ag4(O2C(CF2)2CF3)4(phenazine)2(toluene)]·2(toluene), a phase containing toluene coordinated to Ag(I) in an unusual μ:η1,η1 manner. Solvent-vapour-assisted conversion between the polymorphic coordination polymers and solvent-vapour influence on the conversion of coordination polymers 1 to 2a and 2b is also explored. The transformations have been examined and confirmed by X-ray diffraction, NMR spectroscopy and thermal analyses, including in situ diffraction studies of some transformations.

The coordination polymers [Ag4(O2CCF3)4(phen)3]⋅ phen⋅arene (1⋅phen⋅arene) (phen=phenazine; arene=toluene, p-xylene or benzene) have been synthesised from the solution phase in a series of arene solvents and crystallographically characterised. By contrast, analogous syntheses from o-xylene and m-xylene as the solvent yield the solvent-free coordination polymer [Ag4(O2CCF3)4(phen)2] (2). Toluene, p-xylene and benzene have been successfully used in mixed-arene syntheses to template the formation of coordination polymers 1⋅phen⋅arene, which incorporate o- or m-xylene. The selectivity of 1⋅phen⋅arene for the arene guests was determined, through pairwise competition experiments, to be p-xylene>toluene≈benzene>o-xylene>m-xylene. The largest selectivity coefficient was determined as 14.2 for p-xylene:m-xylene and the smallest was 1.0 for toluene:benzene.

Control of intermolecular interactions is integral to harnessing self-assembly in nature. Here we demonstrate that control of the competition between hydrogen bonds and halogen bonds, the two most highly studied directional intermolecular interactions, can be exerted by choice of solvent (polarity) to direct the self-assembly of co-crystals. Competitive co-crystal formation has been investigated for three pairs of hydrogen bond and halogen bond donors, which can compete for a common acceptor group. These competitions have been examined in seven different solvents. Product formation has been determined and phase purity has been examined by analysis of powder X-ray diffraction patterns. Formation of hydrogen-bonded co-crystals is favoured from less polar solvents and halogen-bonded co-crystals from more polar solvents. The solvent polarity at which the crystal formation switches from hydrogen-bond to halogen-bond dominance depends on the relative strengths of the interactions, but is not a function of the solution-phase interactions alone. The results clearly establish that an appreciation of solvent effects is critical to obtain control of the intermolecular interactions.

Two M8L12 cubic coordination cages, as desolvated crystalline powders, preferentially adsorb CO2 over N2 with ideal selectivity CO2/N2 constants of 49 and 30 at 298 K. A binding site for CO2 is suggested by crystallographic location of CS2 within the cage cavity at an electropositive hydrogen-bond donor site, potentially explaining the high CO2/N2 selectivity compared to other materials with this level of porosity.

Cocrystal formation is considered as one of the most effective solid-state methods to alter the physicochemical properties of active pharmaceutical ingredients (APIs). In silico methods for cocrystal prediction are mostly based on structural and energetic considerations. We have developed a computational method that ranks the probability of cocrystal formation of APIs with large databases of crystal coformers (CCFs). This approach is based on using molecular electrostatic potential surfaces to assess molecular complementarity between two cocrystal components. The screening tool was applied to two low solubility drugs, namely griseofulvin and spironolactone. Promising coformer candidates were selected from a database of 310 pharmaceutically acceptable CCFs, and experimental screening was carried out. Novel solid forms were obtained by liquid-assisted grinding and were characterised by XRPD, DSC, TGA and IR. One new cocrystal of griseofulvin and two new cocrystals of spironolactone were identified, and the crystal structures were determined from the XRPD patterns. For these systems, phenols tend to act as successful H-bond donors in forming cocrystals, while carboxylic acids only give rise to physical mixtures of the two components.

We present the evaluation of the student response to a novel form of practical assessment; the Practical Skills Portfolio (PSP).  The PSP is a concise record of a practical activity for the purposes of assessment, which prompts students to engage in reflective practice on laboratory skills, and provides opportunities for enhanced feedback delivered in a timely manner.  Key goals of this new approach are to assist students in assimilating the practical skills they are developing during their studies and to support them in developing their ability to write the different components of a full lab report.

An extensive study has been conducted into the experiences of Chinese chemistry students studying on transnational education (TNE) programs at four UK institutions partnered with Chinese universities; in particular, student expectations regarding studying in the UK compared with reality were examined. Students were consulted by questionnaire both before and after arrival in the UK. Results from the questionnaires were statistically analysed, the free text responses coded and these data were used to inform further discussion in focus groups. The main differences between the UK and China fell into three key areas: the language barrier; study habits of TNE students in the UK compared to when in China; and the relationship between UK academic staff and the TNE students. These findings are discussed in more detail throughout this paper. We conclude by providing recommendations for other institutions establishing TNE courses.

The validity of a conjecture concerning the asymptotic behavior of a singly-occupied atomic orbital of type nℓ outside an N-electron core, upon approaching the critical charge (below which this electron is not bound), is definitively demonstrated. According to this conjecture, this orbital becomes an infinitely diffuse hydrogenic orbital of type (n − nℓ)ℓ, where nℓ is the number of occupied (or partially occupied) core subshells with angular momentum ℓ. An indicator of this asymptotic behavior is the asymptotic value of the corresponding quantum defect lim Z → N δ n ℓ = n ℓ . To establish this limiting behavior for several singly-excited states of the two-electron atom, we apply the explicitly correlated Hylleraas-type variational exponential expansion to evaluate highly precise energies, that allow the critical charge (Zc = 1) to be approached much more closely than ever before. The results suggest a refinement of the asymptotic form of the quantum defects in the various states considered, exhibiting the distinct origins of s-p splitting versus singlet-triplet splitting.

A new strategy is reported for intramolecular Buchner-type reactions using PIDA as a promotor. Traditionally, the Buchner reaction is achieved via Rh-carbenoids derived from RhII catalysts with diazo compounds. Herein, the first metal-free Buchner-type reaction to construct highly strained cycloheptatriene- and cyclopropane-fused lactams is presented. The advantage of these transformations is in their mild reaction conditions, simple operation, broad functional group compatibility and rapid synthetic protocol. In addition, scaled-up experiments and a series of follow-up synthetic procedures were performed to clarify the flexibility and practicability of this method. DFT calculations were carried out to clarify the mechanism.

Two-dimensional coordination polymers exhibit ligand extrusion into the vapour phase on heating to undergo an extensive structural reorganisation involving bond breaking and formation, ligand migration and reorientation. The reactions occur with retention of crystallinity and have been followed in situ by PXRD.

An electrochemical protocol for the selective oxidation of sulfides to sulfoxides has been developed in which NaCl plays a dual role: (1) as an electrolyte for the electrochemical transformations and (2) as a redox mediator to avoid oxidation of sensitive functional groups. Instead of a traditional oxidant, this methodology utilised traceless electrons as an ideal oxidant using anodic oxidation to access sulfoxides in good to excellent yields at ambient temperature. This metal-free electrochemical protocol is simple, environmentally friendly, and compatible with various sensitive functional groups using mixed acetone/water as the green solvent. Moreover, the cost-effective graphite felt electrodes can be reused up to ten times without loss of electrochemical activity. The methodology could be easily conducted on a gram or even a decagram scale.

An electrochemical protocol for the synthesis of 2,3-disubstituted quinolines by reacting benzoxazinones with arylsulfonyl hydrazides was established under simple and mild conditions (room temperature and an undivided cell). The methodology does not require noble catalysts or external oxidants, providing a green and mild pathway for de novo synthesis of functional quinolines with excellent regioselectivity. Moreover, the method tolerated a variety of functional groups. Notably, the scaled-up experiment and follow-up procedures demonstrate the practicality of electrochemical synthesis.