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Human Papillomavirus (HPV) is the leading cause of cervical cancer, with only some HPV types prevented with vaccines and no treatments for the viral infection itself. One way to target viral infection is by inhibiting the assembly of the L1 monomer into a pentamer, which forms the viral capsid. Four calix[4]arene compounds functionalised with D- and L-aspartic and glutamic acid and an iminodiacetic functionalised calix[4]arene were synthesised and tested for L1 pentamer formation inhibition. The amino acid functionalised calix[4]arene derivatives showed millimolar inhibition (IC50 = 0.72 to 2.67 mM) of pentamer formation, with little difference between the stereoisomers. The iminodiacetic acid calix[4]arene derivative showed no inhibitory properties, despite sharing structural similarities with the four other calix[4]arenes. Confirmation of binding the negatively charged compounds to the positive residues of the L1 protein was achieved by trypsin digestion. This study is helpful in the development of cost-effective inhibitors to prevent HPV assembly.

The synthesis of a novel Rh(i)-Aryl complex is detailed and its ability to serve as an initiator in the stereospecific polymerisation of phenylacetylene evaluated. Targeting the Rh(i) species, (2-phenylnaphthalen-1-yl)rhodium(i)(2,5-norbornadiene)tris(para-fluorophenylphosphine), Rh(nbd)(P(4-FC6H4)3)(2-PhNapth), following recrystallization we obtained the isomeric (2-(naphthalen-2-yl)phenyl)rhodium(i) complex, Rh(nbd)(P(4-FC6H4)3)(2-NapthPh), as determined by X-ray single-crystal structure analysis, and confirmed by X-ray powder diffraction. The isolation of the latter species was proposed to occur from the target (2-PhNapth) derivative via an intramolecular 1,4-Rh atom migration. This supposition was supported by density functional theory (DFT) calculations that indicated the isolated (2-NapthPh) derivative has lower energy (-19 kJ mol-1) than the targeted complex. The structure of the isolated (2-NapthPh) species was confirmed by multinuclear NMR spectroscopy including 2D 31P-103Rh{1H, 103Rh}, heteronuclear multiple-quantum correlation (HMQC) experiments; however, NMR analysis indicated the presence of a second, minor species in solution in an approximate 1:4 ratio with the 2-NapthPh complex. The minor species was identified as a second structural isomer, the 3-phenylnaphthyl derivative, proposed to be formed under a dynamic equilibrium with the 2-NapthPh derivative via a second 1,4-Rh atom migration. DFT calculations indicate that this 1,4-migration proceeds through a low-energy pathway involved in the oxidative addition of a C-H bond to Rh followed by a reductive elimination with the distribution of the products being thermodynamically controlled. The recrystallized Rh(nbd)(P(4-FC6H4)3)(2-NapthPh) complex was subsequently evaluated as an initiator in the polymerisation of phenylacetylene (PA); gratifyingly, the Rh(i) species was an active initiating species with the pseudo-first-order kinetic and molecular weight evolution vs time plots both linear implying a controlled polymerisation while yielding (co)polymers with low dispersities (= Mw/Mn typically ≤1.25) and high cis-Transoidal stereoregularity (>95%). Typical initiation efficiencies, while not quantitative (as judged by size exclusion chromatography), were nonetheless high at ca. 0.8. The presence of the minor 3-phenylnaphthyl species when in solution is proposed to be the cause of the observed non-quantitative initiation.

The reaction of the β-triketonate ligands tris(4-methylbenzoyl)methanide and tribenzoylmethanide with the trivalent lanthanoids Eu3+, Er3+, and Yb3+ in the presence of Cs+ afforded polymeric structures where the repeating units are represented by bimetallic tetranuclear assemblies of formulation [Ln(Cs)(β-triketonate)4]2n. The only exception is the structure formed by the reaction of tris(4-methylbenzoyl)methanide, Yb3+, and Cs+, which yielded a polymeric assembly where the repeating units are mononuclear Yb3+ complexes bridged by Cs+ cations. Photophysical measurements on the obtained materials confirmed efficient sensitization from the ligand excited states to the 4f∗ excited states of the three lanthanoids. According to transient absorption data, Er3+ and Yb3+ are sensitized via energy transfer from the triplet state of the β-triketonate ligands. On the other hand, energy transfer to Eu3+ seems to occur via an alternative pathway, possibly directly via the singlet state or through ligand to metal charge transfer states. The emission measurements confirm efficient sensitization for all three lanthanoids and bright near-infrared emission for Er3+ and Yb3+, a characteristic that seems to be linked to the specific chemical structure of the β-triketonate ligands.

This work is supported by the Australian Research Council and a Royal Society International Exchanges Grant. EZ-C thanks EPSRC (EP/M02105X/1) for support. LAG and BLR thank Curtin University for the postgraduate scholarship. The authors acknowledge access to the facilities at the Centre for Microscopy, Characterisation and Analysis, University of Western Australia The reaction of the β-triketonate ligands tris(4-methylbenzoyl)methanide and tribenzoylmethanide with the trivalent lanthanoid Eu3+, Er3+, and Yb3+ in the presence of Cs+ afforded polymeric structures where the repeating units are represented by bimetallic tetranuclear assemblies of formulation {[Ln(Cs)(β-triketonate)4]2}n. The only exception is the structure formed by reaction of tris(4-methylbenzoyl)methanide, Yb3+, and Cs+, which yielded a polymeric assembly where the repeating units are mononuclear Yb3+ complexes bridged by Cs+ cations. Photophysical measurements on the obtained materials confirmed efficient sensitization from the ligand excited states to the 4ƒ* excited stated of the three lanthanoids. According to transient absorption data, Er3+ and Yb3+ are sensitized via energy transfer from the triplet state of the β-triketonate ligands. On the other hand, energy transfer to Eu3+ seems to occur via an alternative pathway, possibly directly via the singlet state or through ligand-to-metal charge transfer states. The emission measurements confirm efficient sensitization for all three lanthanoids and bright near-infrared emission for Er3+ and Yb3+, a characteristic that seems to be linked to the specific chemical structure of the β-triketonate ligands. Publisher PDF