Characterisation of new compounds
It is the responsibility of authors to provide fully convincing evidence for the homogeneity, purity and identity of all compounds they claim as new. This evidence is required to establish that the properties and constants reported are those of the compound with the new structure claimed.
Referees will assess, as a whole, the evidence presented in support of the claims made by the authors. The requirements for characterisation criteria are detailed below.
Authors are required to provide unequivocal support for the purity and assigned structure of all compounds using a combination of the following characterisation techniques.
- Elemental analysis (within ±0.4% of the calculated value) is required to confirm 95% sample purity and corroborate isomeric purity.
- Authors are requested to provide copies of 1H,13C NMR spectra and/or GC/HPLC traces; however, if satisfactory elemental analysis cannot be obtained copies of these spectra and/or traces must be provided.
- High-resolution mass spectra are acceptable as proof of the molecular weight providing the purity of the sample has been accurately determined using one of these techniques.
- For libraries of compounds, HPLC traces should be submitted as proof of purity.
- The determination of enantiomeric excess of nonracemic, chiral substances should be supported with either GC/HPLC traces with retention times for both enantiomers and separation conditions (that is, chiral support, solvent and flow rate) or for Mosher Ester/Chiral Shift Reagent analysis, copies of the spectra.
- Important physical properties, for example, boiling or melting point, specific rotation, refractive index, including conditions and a comparison to the literature for known compounds, should be provided. For crystalline compounds, the method used for recrystallisation should also be documented (that is, solvent etc.).
- Mass spectra and a complete numerical listing of 1H,13C NMR peaks in support of the assigned structure, including relevant 2D NMR and related experiments (that is, NOE, etc.) is required. Authors are requested to provide copies of these spectra.
- Infra red spectra that support functional group modifications, including other diagnostic assignments, should be included.
For all soluble polymers, an estimation of molecular weight must be provided by a suitable method - for example, size exclusion chromatography, including details of columns, eluents and calibration standards, intrinsic viscosity, MALDI TOF, etc.
In addition, full NMR characterisation (1H,13C) as for organic compound characterisation should be included. Small molecules on the route to the polymers should be characterised as above and NMR data should be tabulated.
Inorganic and organometallic compounds
A new chemical substance (molecule or extended solid) should have a homogeneous composition and structure. Where the compound is molecular, authors must provide data to unequivocally establish its homogeneity, purity and identification. In general, this should include elemental analyses that agree to within Â±0.4% of the calculated values.
In cases where elemental analyses cannot be obtained (for example, for thermally unstable compounds), justification for the omission of this data should be provided. Note that an X-ray crystal structure is not sufficient for the characterisation of a new material, since the crystal used in this analysis does not necessarily represent the bulk sample.
In rare cases, it may be possible to substitute elemental analyses with high-resolution mass spectrometric molecular weights. This is appropriate, for example, with trivial derivatives of thoroughly characterised substances or routine synthetic intermediates.
In all cases, relevant spectroscopic data (NMR, IR, UV-vis, etc.) should be provided in tabulated form or as reproduced spectra. These may be relegated to the electronic supplementary information (ESI) to conserve journal space. However, it should be noted that, in general, mass spectrometric and spectroscopic data do not constitute proof of purity, and, in the absence of elemental analyses, additional evidence of purity should be provided (melting points, PXRD data, etc.).
Where the compound is an extended solid, it is important to unequivocally establish the chemical structure and bulk composition. Single crystal diffraction does not determine the bulk structure. Referees will normally look to see evidence of bulk homogeneity.
A fully indexed powder diffraction pattern which agrees with single crystal data may be used as evidence of a bulk homogeneous structure and chemical analysis may be used to establish purity and homogeneous composition.
If data from magnetic measurements are presented, the manuscript must provide a thorough description of the experimental details pertaining to how the sample was measured (in a gelatin capsule, Teflon capsule, as a powder, etc).
If the data have been corrected for sample or sample-holder diamagnetism, the diamagnetic correction term must be provided and the manner in which it was determined (for example, calculated using Pascal's constants, measured) must be stated.
Any fit of magnetic data to an analytical expression must be accompanied by the Hamiltonian from which the analytical expression is derived, the analytical expression itself, and the fitting parameters. If the expression is lengthy, it may be included in the electronic supplementary information instead of within the main manuscript text. Its inclusion as supplementary information should be noted in the ESI paragraph at the end of the manuscript. When an exchange coupling constant (J) is quoted in the abstract, the form of the Hamiltonian must also be included in the abstract.
Nano-sized materials (such as quantum dots, nanoparticles, nanotubes, nanowires)
It is essential that the authors not only provide detailed characterisation on individual objects but also a comprehensive characterisation of the bulk composition. Characterisation of the bulk of the sample could require determination of the chemical composition and size distribution over large portions of the sample.
Biomolecules (for example, enzymes, proteins, DNA/RNA, oligosaccharides, oligonucleotides)
Authors should provide rigorous evidence for the identity and purity of the biomolecules described.
The techniques that may be employed to substantiate identity include mass spectrometry, LC-MS, sequencing data (for proteins and oligonucleotides), high field 1H,13C NMR spectroscopy, or X-ray crystallography.
Purity must be established by one or more of the following: HPLC, gel electrophoresis, capillary electrophoresis, or high field 1H,13C NMR spectroscopy. Sequence verification also needs to be carried out for nucleic acid cases involving molecular biology including all mutants; for new protein or gene sequences, the entire sequence must be provided.
For organic synthesis involving DNA, RNA oligonucleotides, their derivatives or mimics, purity must be established using HPLC and mass spectrometry as a minimum.
For new derivatives comprising modified monomers, the usual organic chemistry analytical requirements for the novel monomer must be provided. However, it is not necessary to provide this level of characterisation for the oligonucleotide into which the novel monomer is incorporated.
Authors must provide sufficient information to enable readers to reproduce any computational results. If software was used for calculations and is generally available, it must be properly cited in the notes and references. References to the methods upon which the software is based must also be provided.
Equations, data, geometric parameters/coordinates, or other numerical parameters essential to reproduction of the computational results (or adequate references when available in the open literature) must be provided.
Authors who report the results of electronic structure calculations in relative energies should also include in ESI the absolute energies obtained directly from the computational output files.
Computational results obtained using methods, parameters, or input data that are not adequately described in the manuscript or in the referenced literature are not acceptable for publication.
Where the screening of new catalysts is reported, authors should provide a mass balance for all reactions (using, for example, an internal standard in their analysis technique). Recycling efficiencies should be based on reaction rates measurements and not product yield as a function of cycle.