The Same but Different: Isostructural Polymorphs and the Case of 3‑Chloromandelic Acid

The expression “isostructural polymorphs” would appear to be an impossible combination of two mutually incompatible words. “Isostructural” implies a high degree of structural similarity; however, conversely, “polymorph” implies structural distinguishability. The structures of two newly determined polymorphs of 3-chloromandelic acid nevertheless justify the use of this expression, for they differ only in crystal symmetry and hardly at all in molecular position or conformation within the crystalline lattice. We demonstrate that parameters derived by the XPac program can be useful in establishing the limits of isostructurality

Design of Cocrystals for Molecules with Limited Hydrogen Bonding Functionalities: Propyphenazone as a Model System

We report eight new cocrystals with an analgesic drug, propyphenazone, which belongs to a family of compounds that possess limited or no hydrogen bonding functionality. Such molecules present difficulties in predicting and selecting appropriate coformers for potential multicomponent systems, and current prediction methodologies are unsuitable due to their focus around hydrogen bonding. This study used a knowledge-based strategy to identify appropriate coformers as well as testing a wide variety of molecules to confirm the initial predictions. All new cocrystals were characterized using X-ray diffraction techniques as well as measuring their physicochemical properties. These included the thermal behavior, stability under slurry and accelerated conditions, and solubility and dissolution rate and were compared with the parent propyphenazone. It was found that while the stability of most of the cocrystals and propyphenazone were comparable, a cocrystal with hydroquinone showed an increase in both the solubility and dissolution rate of propyphenazone

Twists and Turns of Platinum-Allene Complexes: NMR Techniques for the Study of the Dynamic Behavior in Solution

Classic (dynamic exchange line-shape analysis) and novel (SSTD NMR) NMR techniques have been applied in order to obtain the kinetic and thermodynamic parameters of the three main processes occurring in the fluxional behavior of Pt-allene complexes with <i>N</i>-containing ligands, in four and five coordination mode, in solution. Our results show intramolecular helical and rotational movements closely related to each other, confirming η¹-staggered structures as possible intermediates. The ligand exchange in these complexes seems to occur via a ligand-independent dissociative mechanism, where coordinating solvents might be involved in the stabilization of the intermediates. The differences observed in the interaction of allenes with other metals could be the basis to explain the divergent reactivity observed in platinum-catalyzed processes

Creating Context for the Experiment Record. User-Defined Metadata: Investigations into Metadata Usage in the LabTrove ELN

The drive toward more transparency in research, the growing willingness to make data openly available, and the reuse of data to maximize the return on research investment all increase the importance of being able to find information and make links to the underlying data. The use of metadata in Electronic Laboratory Notebooks (ELNs) to curate experiment data is an essential ingredient for facilitating discovery. The University of Southampton has developed a Web browser-based ELN that enables users to add their own metadata to notebook entries. A survey of these notebooks was completed to assess user behavior and patterns of metadata usage within ELNs, while user perceptions and expectations were gathered through interviews and user-testing activities within the community. The findings indicate that while some groups are comfortable with metadata and are able to design a metadata structure that works effectively, many users are making little attempts to use it, thereby endangering their ability to recover data in the future. A survey of patterns of metadata use in these notebooks, together with feedback from the user community, indicated that while a few groups are comfortable with metadata and are able to design a metadata structure that works effectively, many users adopt a “minimum required” approach to metadata. To investigate whether the patterns of metadata use in LabTrove were unusual, a series of surveys were undertaken to investigate metadata usage in a variety of platforms supporting user-defined metadata. These surveys also provided the opportunity to investigate whether interface designs in these other environments might inform strategies for encouraging metadata creation and more effective use of metadata in LabTrove

Phosphorescent, Cyclometalated Cinchophen-Derived Platinum Complexes: Syntheses, Structures, and Electronic Properties

The syntheses of nine new monometallic heteroleptic platinum complexes [Pt­(<b>L1–4</b>)­(acac)], [Pt­(<b>L1</b>)­(hmacac/hfacac)], [PtCl­(<b>L1</b>)­(py)], [Pt­(<b>L1</b>)­(8-Q)], [Pt­(<b>L1</b>)­(bpy)]­(PF₆) (where L1 = 2-phenyl-4-ethyl-quinolinecarboxylate; L2/L3 = <i>N</i>-functionalization of 2-phenyl-<i>N</i>-aryl/alkyl-quinoline-4-carboxamides; L4 = 2-phenyl-4-quinolinecarboxylic acid (cinchophen); acac = acetylacetonato; hmacac =2,2,6,6-tetramethyl-3,5-heptanedionate; hfacac = hexafluoroacetylacetonate; py = pyridine; 8-Q = 8-quinolinato; bpy =2,2′-bipyridine) are described from precursor dimeric Pt­(II) species via an intermediate DMSO adduct of the general form [PtCl­(<b>L1–4</b>)­(DMSO)]. Single crystal X-ray diffraction studies were undertaken on three complexes, [Pt­(<b>L1</b>)­(acac)], [PtCl­(<b>L1</b>)­(DMSO)], and [Pt­(<b>L1</b>)­(bpy)]­(PF₆). The structures show that the complexes each adopt a distorted square planar geometry (most severely in the case of [Pt­(<b>L1</b>)­(bpy)]­(PF₆)) with indications of intermolecular Pt–Pt interactions in one example. The complexes were investigated using ¹⁹⁵Pt­{¹H} NMR spectroscopy, revealing varied chemical shifts that were strongly dependent upon the specific coordination environment of Pt­(II). Luminescence studies showed the complexes possess a phosphorescent character with tunable emission wavelengths between 605 and 641 nm and luminescent lifetimes up to ∼450 ns. Supporting TD-DFT studies provided descriptions of the HOMO and LUMO energy levels of the key complex types, confirming an MLCT contribution to the lowest energy absorption that generally correlated well with the experimental spectra. The contribution of the Pt­(5d) center to the calculated HOMOs was strongly ligand dependent, whereas the LUMOs are generally localized over the quinoline component of the cyclometalated ligand

Semipinacol Rearrangement of <i>Cis</i>-Fused β-Lactam Diols into Keto-Bridged Bicyclic Lactams

The 6-azabicyclo[3.2.1]octane ring system, prevalent in a range of biologically active molecules, is prepared through a novel semipinacol rearrangement utilizing a cyclic phosphorane or sulfite intermediate. The rearrangement proceeds with exclusive <i>N</i>-acyl group migration of a β-lactam ring and results in carbonyl functionality at the 7- and bridging 8-position of the bicycle. Precursor ring-fused β-lactam diols are prepared through a sequence of 4-<i>exo trig</i> carbamoyl radical cyclization, regioselective dithiocarbamate group elimination, and dihydroxylation

Semipinacol Rearrangement of <i>Cis</i>-Fused β-Lactam Diols into Keto-Bridged Bicyclic Lactams

The 6-azabicyclo[3.2.1]octane ring system, prevalent in a range of biologically active molecules, is prepared through a novel semipinacol rearrangement utilizing a cyclic phosphorane or sulfite intermediate. The rearrangement proceeds with exclusive <i>N</i>-acyl group migration of a β-lactam ring and results in carbonyl functionality at the 7- and bridging 8-position of the bicycle. Precursor ring-fused β-lactam diols are prepared through a sequence of 4-<i>exo trig</i> carbamoyl radical cyclization, regioselective dithiocarbamate group elimination, and dihydroxylation

Luminescent Pt(II) Complexes Using Unsymmetrical Bis(2-pyridylimino)isoindolate Analogues

A series of ligands based upon a 1,3-diimino-isoindoline framework have been synthesized and investigated as pincer-type (N∧N∧N) chelates for Pt(II). The synthetic route allows different combinations of heterocyclic moieties (including pyridyl, thiazole, and isoquinoline) to yield new unsymmetrical ligands. Pt(L1–6)Cl complexes were obtained and characterized using a range of spectroscopic and analytical techniques: 1H and 13C NMR, IR, UV–vis and luminescence spectroscopies, elemental analyses, high-resolution mass spectrometry, electrochemistry, and one example via X-ray crystallography which showed a distorted square planar environment at Pt(II). Cyclic voltammetry on the complexes showed one irreversible oxidation between +0.75 and +1 V (attributed to Pt2+/3+ couple) and a number of ligand-based reductions; in four complexes, two fully reversible reductions were noted between −1.4 and −1.9 V. Photophysical studies showed that Pt(L1–6)Cl absorbs efficiently in the visible region through a combination of ligand-based bands and metal-to-ligand charge-transfer features at 400–550 nm, with assignments supported by DFT calculations. Excitation at 500 nm led to luminescence (studied in both solutions and solid state) in all cases with different combinations of the heterocyclic donors providing tuning of the emission wavelength around 550–678 nm

Semipinacol Rearrangement of <i>Cis</i>-Fused β-Lactam Diols into Keto-Bridged Bicyclic Lactams

The 6-azabicyclo[3.2.1]octane ring system, prevalent in a range of biologically active molecules, is prepared through a novel semipinacol rearrangement utilizing a cyclic phosphorane or sulfite intermediate. The rearrangement proceeds with exclusive <i>N</i>-acyl group migration of a β-lactam ring and results in carbonyl functionality at the 7- and bridging 8-position of the bicycle. Precursor ring-fused β-lactam diols are prepared through a sequence of 4-<i>exo trig</i> carbamoyl radical cyclization, regioselective dithiocarbamate group elimination, and dihydroxylation

Semipinacol Rearrangement of <i>Cis</i>-Fused β-Lactam Diols into Keto-Bridged Bicyclic Lactams

The 6-azabicyclo[3.2.1]octane ring system, prevalent in a range of biologically active molecules, is prepared through a novel semipinacol rearrangement utilizing a cyclic phosphorane or sulfite intermediate. The rearrangement proceeds with exclusive <i>N</i>-acyl group migration of a β-lactam ring and results in carbonyl functionality at the 7- and bridging 8-position of the bicycle. Precursor ring-fused β-lactam diols are prepared through a sequence of 4-<i>exo trig</i> carbamoyl radical cyclization, regioselective dithiocarbamate group elimination, and dihydroxylation