Novel rhenium(V) nitride complexes with dithiocarbimate ligands: A synchrotron X-ray and DFT structural investigation

The application of rhenium complexes as therapeutic agents in nuclear medicine has propelled research into the chemistry of these compounds. In our effort to develop and investigate new therapeutic radiopharmaceuticals based on the complexes of rhenium we have investigated the nitride core, [ReN]2+. This work looks at the behavior of sulfonamide based dithiocarbimates towards the rhenium(V) nitride core. The aim here was to prepare anionic complexes with aromatic as well as fluorescent aromatic groups in the sulfonamide substituent located on the dithiocarbimate backbone. We envisaged that the polar sulfonamide and dianionic charge would confer solubility in water. Here we report the reactions of the dithiocarbimate ligands towards the rhenium(V) precursors: [ReNCl2(PPh3)2] and [ReNCl2(PMe2Ph)3]. These reactions proceeded with bis-substitution by the dithiocarbimate ligand, resulting in the formation of a dianionic rhenium(V) complex, of the type [ReN(S-S)2]2-, where (S-S) denotes the sulfonamide-tagged dithiocarbimato unit. Spectroscopic characterization data, as well as the synchrotron X-ray diffraction structure of the metal complex with the phenyl sulfonamide backbone shed light into the structural features of this interesting class of ligands and opens up opportunities for further studies in molecular imaging and therapeutic arenas.</p

Explorations into peptide nucleic acid contrast agents as emerging scaffolds for breakthrough solutions in medical imaging and diagnosis

Peptide nucleic acids (PNAs, nucleic acid analogues with a peptide backbone rather than a phosphoribosyl backbone) have emerged as promising chemical agents in antigene or antisense therapeutics, as splicing modulators or in gene editing. Their main benefits, compared to DNA or RNA agents, are their biochemical stability and the lack of negative charges throughout the backbone, leading to negligible electrostatic interaction with the strand with which they are hybridizing. As a result, hybridization of PNA strands with DNA or RNA strands leads to higher binding energies and melting temperatures. A lack of natural transporters, however, necessitates the formation of PNA-containing chimeras or the formulation of nanoparticular cell delivery methods. Here, we set out to explore the progress made in using imaging agents based on PNAs in diagnostic applications and highlight selected developments and challenges

Self-Assembled Materials Incorporating Functional Porphyrins and Carbon Nanoplatforms as Building Blocks for Photovoltaic Energy Applications.

As a primary goal, this review highlights the role of supramolecular interactions in the assembly of new sustainable materials incorporating functional porphyrins and carbon nanoplatforms as building blocks for photovoltaics advancements

Applications of “Hot” and “Cold” Bis(thiosemicarbazonato) Metal Complexes in Multimodal Imaging

The applications of coordination chemistry to molecular imaging has become a matter of intense research over the past 10 years. In particular, the applications of bis(thiosemicarbazonato) metal complexes in molecular imaging have mainly been focused on compounds with aliphatic backbones due to the in vivo imaging success of hypoxic tumors with PET (positron emission tomography) using 64CuATSM [copper (diacetyl-bis(N4-methylthiosemicarbazone))]. This compound entered clinical trials in the US and the UK during the first decade of the 21st century for imaging hypoxia in head and neck tumors. The replacement of the ligand backbone to aromatic groups, coupled with the exocyclic N's functionalization during the synthesis of bis(thiosemicarbazones) opens the possibility to use the corresponding metal complexes as multimodal imaging agents of use, both in vitro for optical detection, and in vivo when radiolabeled with several different metallic species. The greater kinetic stability of acenaphthenequinone bis(thiosemicarbazonato) metal complexes, with respect to that of the corresponding aliphatic ATSM complexes, allows the stabilization of a number of imaging probes, with special interest in “cold” and “hot” Cu(II) and Ga(III) derivatives for PET applications and 111In(III) derivatives for SPECT (single-photon emission computed tomography) applications, whilst Zn(II) derivatives display optical imaging properties in cells, with enhanced fluorescence emission and lifetime with respect to the free ligands. Preliminary studies have shown that gallium-based acenaphthenequinone bis(thiosemicarbazonato) complexes are also hypoxia selective in vitro, thus increasing the interest in them as new generation imaging agents for in vitro and in vivo applications.</p

Investigations into the reactivity of lithium indenyl with alpha diimines with chlorinated backbones and formation of related functional ligands and metal complexes

Reaction between lithium indenyl and a chlorine substituted alpha diimine of the form [{Cl(NPh)2}C)]2 unexpectedly yielded the corresponding NH rearranged derivative [PhN(H)C(C9H6)]2 (1) rather than the predicted symmetrical α-diimine. This compound 1 was characterised by 1H NMR, 13C{1H} NMR and mass spectrometry, and additionally by X-ray diffraction. It was found that 1 was the first indene-substituted and symmetric secondary amine which was also highly fluorescent in DMSO. The reactivity of 1 towards simple inorganic and organometallic transition metals precursors based on the MX2 fragments, where M = Group 10 metals and X = halides or methyl groups, has been investigated. Surprisingly, the reaction with [PtMe2(COD)] led to the coupling reaction between the indenyl groups incorporated at the C-C ligand backbone and a new ligand (2) was discovered, in an attempt to synthesise the metal-linked diamine. Single crystal X-ray diffraction studies confirm this compound 2 to feature coupled indenyl residues and delocalised C-C bonds in the solid state. Structural authentication by X-ray crystallography showed compound 2 to be a very rare example of flat and extended aromatic organic molecule and mass spectrometry, IR and NMR spectroscopy were carried out to gain further insight into the solid state and solution phase structures. Further experiments to synthesise analogues of [PhN(H)C(Ind)]2 aiming to shift a likely equilibrium in favour the imine tautomer, by introducing bulky ortho substituents onto the benzene ring (R = Me, iPr) showed the presence of the imine tautomer to be increasingly favoured in 1H NMR spectra, with an increase in the steric bulk of the ortho substituents. However, the enamine tautomer is still observed to a minor extent even with isopropyl substituents and yields of these desired compounds were low on steric grounds.</p

Interactions between an aryl thioacetate-functionalized Zn(II) porphyrin and graphene oxide

The surface modification of graphene oxide (GO) is carried out via the supramolecular functionalization route using a Zn(II)-porphyrin which is soluble in common organic solvents on basis of long alkyl chains present at the exocyclic positions. This acts as a dispersing agent and decorates the surface of the graphene oxide uniformly, giving rise to a new nanohybrid denoted Zn(II)-porphyrin@GO. The resulting Zn(II)-porphyrin@GO nanohybrid forms a stable dispersion in ethanol (as characterized by several different spectroscopic techniques such as UV–vis, Fourier transform infrared, Raman). The morphology of Zn(II)-porphyrin@GO nanohybrid is investigated by atomic force microscopy (AFM) and transmission electron microscope (TEM)/selected area electron diffraction. Both TEM and AFM measurements indicate that the Zn(II)-porphyrin self-assemble onto the surface of graphene oxide sheets. Steady-state and time-resolved fluorescence emission studies in the dispersed phase, and as a thin film, point toward the strongly quenched fluorescence emission and lifetime decay, suggesting that energy transfer occurs from the singlet excited state of Zn(II)-porphyrin unit to GO sheets

Novel rhenium(V) nitride complexes with dithiocarbimate ligands: A synchrotron X-ray and DFT structural investigation

The application of rhenium complexes as therapeutic agents in nuclear medicine has propelled research into the chemistry of these compounds. In our effort to develop and investigate new therapeutic radiopharmaceuticals based on the complexes of rhenium we have investigated the nitride core, [ReN]2+. This work looks at the behavior of sulfonamide based dithiocarbimates towards the rhenium(V) nitride core. The aim here was to prepare anionic complexes with aromatic as well as fluorescent aromatic groups in the sulfonamide substituent located on the dithiocarbimate backbone. We envisaged that the polar sulfonamide and dianionic charge would confer solubility in water. Here we report the reactions of the dithiocarbimate ligands towards the rhenium(V) precursors: [ReNCl2(PPh3)2] and [ReNCl2(PMe2Ph)3]. These reactions proceeded with bis-substitution by the dithiocarbimate ligand, resulting in the formation of a dianionic rhenium(V) complex, of the type [ReN(S-S)2]2-, where (S-S) denotes the sulfonamide-tagged dithiocarbimato unit. Spectroscopic characterization data, as well as the synchrotron X-ray diffraction structure of the metal complex with the phenyl sulfonamide backbone shed light into the structural features of this interesting class of ligands and opens up opportunities for further studies in molecular imaging and therapeutic arenas.</p

Tripodal BODIPY-tagged and functional molecular probes: synthesis, computational investigations and explorations by multiphoton fluorescence lifetime imaging microscopy

A range of novel BODIPY derivatives with a tripodal aromatic core was synthesized and characterized spectroscopically. These new fluorophores showed promising features as probes for in vitro assays in live cells and offer strategic routes for further functionalization towards hybrid nanomaterials. Incorporation of biotin tags facilitated proof-of-concept access to targeted bioconjugates as molecular probes. Computational explorations using DFT and TD-DFT calculations identified the most stable tripodal linker conformations and predicted their absorption and emission behavior. The uptake and speciation of these molecules in living prostate cancer cells was imaged by single- and two-photon excitation techniques coupled with two-photon fluorescence lifetime imaging (2P FLIM)The authors thank the ERC for funding through the Consolidator Grant O2Sense (617107), ERC PoC Tools-To-Sense (963937), and the University of Bath for the URSA-Science Strategic PhD studentship to ML. SIP also thanks the following grants for funding: STFC CDN+ Biosensing and NIR Imaging of New Biomarkers for Prostate Cancer, BBSRC (BB/W019655/1: Multi User High- Content Confocal Fluorescence Microscope); EP/K0171 60/1: ‘New manufacturable approaches to the deposition and patterning of graphene materials’; EP/L016354/1: EPSRC Centre for Doctoral Training in Sustainable Chemical Technologies EP/ G03768X/1: Doctoral Training Centre in Sustainable Chemical Technologies. DGC thanks to the Ministerio de Ciencia, Innovaci' on y Universidades (Spain) for funding (TED2021132779B-100 and TED2021-129876B I00