Methoxy-phenyl groups reduce the cytotoxicity and increase the aqueous solubility of phosphonium zwitterions and salts

The ability of phosphonium cations to act as intracellular transport vectors is well-established. Previous research has demonstrated that phosphonioalkylthiosulfate zwitterions, and -thioacetylalkylphosphonium salts are useful precursors for the formation of phosphonium-functionalised gold nanoparticles and enable the nanoparticles to be transported into cells for diagnostic and therapeutic purposes. In this report we describe the synthesis and characterisation of a series of phosphonioalkylthiosulfate zwitterions, and-thioacetylalkylphosphonium salts derived from the methoxy-phenylphosphines tris(2,4,6-trimethoxyphenyl)phosphine, tris(2,6-dimethoxyphenyl)phosphine and tri(4-methoxyphenyl)phosphine. The methoxyphenyl-substituted phosphonium compounds show greater solubility in aqueous systems than the corresponding phenyl derivatives and cytotoxicity studies reveal that the compounds are significantly less toxic than the related triphenylphosphonium derivatives. The solid-state structures of the tris(2,4,6-trimethoxyphenyl)- and tris(2,6-dimethoxyphenyl)-phosphoniopropylthiosulfate zwitterions have been investigated by single crystal X-ray crystallography. The differences in the molecular packing of the compounds may account for greater solubility of these zwitterions in aqueous solutions

Reaction of thiones with dihalogens: comparison of the solid state structures of 4,5-bis(methylsulfanyl)-1,3-dithiole-2-thione-diiodine, -dibromine and -iodine monobromide

Reaction of 4,5-bis(methylsulfanyl)-1,3-dithiole-2-thione 1 with diiodine or iodine monobromide in CH2Cl2 resulted in the formation of molecular charge-transfer complexes 1 . I-2 and 1 . IBr respectively. Both complexes have been characterised crystallographically and contain a linear S-I-X (X = I or Br) moiety with the sulfur adopting a tetrahedral geometry taking into account the stereochemically active lone pairs. The S-I [2.716(3)] and I-I [2.808(3) Angstrom] bond lengths in 1 . I-2 are similar to those reported for diiodine complexes of related thione donors. The adduct 1 . IBr is the first crystallographically characterised thione-iodine monobromide charge-transfer complex. The S-I distance [2.589(2) Angstrom] is shorter than that in 1 . I-2, consistent with IBr being a stronger acceptor than I-2. The I-Br distance [2.7138(11) Angstrom] is lengthened with respect to that in unco-ordinated IBr, but within bonding distance when compared to the sum of the van der Waals radii for iodine and bromine (3.75 Angstrom). Treatment of 1 with dibromine under identical conditions resulted in the formation of the adduct 1 . Br-2 and the dithiolylium salt [C5H6S4Br][Br-3]. 1/2Br(2) 2. Treatment of 1 with Br-2 in toluene led to the isolation of 1 . Br-2 only. The crystal structure of 1 . Br-2 shows the compound to contain a linear Br-S-Br moiety with the sulfur in a T-shaped or Psi-trigonal bipyramidal environment (taking into account the stereochemically active lone pairs). The structure of 2 reveals a three component system consisting of the [C5H6S4Br](+) cation, the [Br-3](-) anion and a molecule of Br-2 in a 2:2:1 ratio. These components are held in the lattice by a series of weak intermolecular interactions which link the tribromide ions and dibromine molecules into zigzag chains

Omega-thioacetylalkylphosphonium salts: precursors for the preparation of phosphonium-functionalised gold nanoparticles

Two new omega-thioacetylalkylphosphonium salts that function as masked cationic alkanethiolate ligands for the stabilisation of gold nanoparticles have been prepared. Both (3-thioacetylpropyl) triphenylphosphonium bromide and (6-thioacetylhexyl) triphenylphosphonium bromide were shown to form water-soluble gold nanoparticles of ca. 5-10 nm in size that are stable for up to six months. The related (3-thioacetylpropyl) diphenylphosphine oxide was also prepared but did not act as a stabilising ligand in gold nanoparticle formation

The synthesis and characterisation of masked phosphonioalkyl selenoates: potential ligands for the production of functionalised gold nanoparticles

Two new masked phosphonioalkylselenoate ligands, bis(3-triphenylphosphoniopropyl)diselenide- and 6-(selenocyano)hexyl-triphenylphosphonium-selenocyanates, have been prepared. The molecular structure of the bis(3-triphenylphosphoniopropyl)diselenide diselenocyanate has been determined by X-ray crystallography. The structure reveals an overall stoichiometry of {[Ph3P+(CH2)3Se]2(SeCN?)2 · KOH}, with the bis(3-triphenylphosphoniopropylselenium)diselenocyanate units arranged in pairs around an inversion centre. The potassium ion is disordered over several positions but its main component forms a near linear KSe contact to one of the selenium atoms in the diselenide bond. The hexyl derivative, 6-(selenocyano)hexyl-triphenylphosphonium selenocyanate forms as a yellow oil that was characterised spectroscopically. Both phosphonioalkylselenide cations undergo reductive cleavage to form phosphonioalkylselenoate zwitterions. Attempts to prepare phosphonioalkylselenoate-functionalised gold nanoparticles in situ through the NaBH4-promoted reduction of tetrachloroaurate salts in a water/dichloromethane biphasic system are also described

Novel transition metal complexes based on covalently linked DMIT systems

The synthesis of a novel series of transition metal ligands and complexes is reported; the materials are related to the well-studied DMIT systems, allowing greater versatility in terms of structural design and processability

Self-assembly of halogen adducts of ester and carboxylic acid functionalised 1,3-dithiole-2-thiones

New halogen adducts of 1,3-dithiole-2-thione-4-carboxylic acid and dimethyl 1,3-dithiole-2-thione-4,5-dicarboxylate have been prepared and characterised by X-ray crystallographic studies. The adducts feature an array of intramolecular and intermolecular close contacts involving chalcogen-chalcogen, chalcogen-halogen and halogen-halogen interactions. Whilst these contacts are derived from the basic heterocyclic unit and the coordinated halogen molecules, the ester and acid functionalities provide a varied and rich array of hydrogen bonding motifs, which significantly enhance the long-range order of the supramolecular structures