Infrared spectra of KNaSO4 and K3Na(SO4)2

The infrared spectra, transmittance and polarized reflectance, of KNaSO₄ and K₃Na(SO₄)₂ are reported. Group theoretical analysis was carried out and a vibrational assignment proposed on basis of C_3v and D_3d symmetries. Factor group and site effects are discussed.     

Infrared spectra of Cs3CoCl5

The infrared spectra, transmittance, and polarized reflectance of Cs₃CoCl₅ are reported. The group theoretical analysis was executed and a vibrational assignment proposed on the basis of D_4h symmetry. Factor group and site effects are discussed.     

Reaction of Ru3(CO)12 with but-2-yn-1,4-diol in CH3OH/KOH solution. Crystal structure of (μ-Cl)Ru3(CO)9[μ3-η-H2CCC(H)CH2]

The reaction of Ru₃(CO)₁₂ with but-2-yn-1,4-diol (HOCH₂CCCH₂OH, BUD) in CH₃OH/KOH followed by acidification with HCl leads to four products, one of which has been identified as the title complex (μ-Cl)Ru₃(CO)₉[μ₃-η⁴-H₂CCC(H)CH₂]. This is an open cluster containing a bridging Cl atom on the open side and a C₄H₅ moiety bound to all the metals. The structure of the complex has been determined by X-ray analysis.The thermal reaction of Ru₃(CO)₁₂ with BUD has been revisited for a comparison with the results in alkaline solution. The main product is the allylic derivative HRu₃(CO)₉[HCCHCCHO].     

A macrocyclic ligand able to bind gallium(III) by preorganized pendant arms; coordination and kinetic studies

The equilibria and kinetics of the binding of gallium(III) to 4-(N),10-(N)-bis[2-(3-hydroxo-2-oxo-2-H-pyridine-1-y1)acetamido]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane (L) were investigated in acidic medium at ionic strength 1 M (NaClO4). Spectrophotometric titrations in the UV region revealed that L is able to bind Ga3+ also at high H+ concentration. The kinetic (stopped-flow) experiments are interpreted on the basis of three parallel reaction paths (i) M3+ + H2L2+ = M(H2L)5+ where M(H2L)5+ is in a steady state, (ii) M(OH)2+ + H2L2+ = M(HL)4+ + H2O and (iii) M(OH)2+ + HL+ = ML3+ + H2O. The first-order rate constants for conversion of the outer-sphere into the inner-sphere complexes are similar to those of the Ga(III)/tropolone system which is known to react according to the dissociative Id mechanism and to the relevant rate constants for water exchange at the metal ion. The effects of pH on the UV-Vis absorption, fluorescence emission properties and NMR spectral features on the Ga(III)/L system were also investigated. Spectrophotometric titrations in the UV region reveal that, in acid medium the prevailing species is M(HL)4+ whereas the chelate ML3+ prevails for [H+] < 0.01 M. The results indicate metal coordination at the oxygen atoms of the 3-hydroxo-2-oxopyridine residues.     

Mechanistic aspects of the interaction of intercalating metal complexes with nucleic acids

Since the discovery of the intercalative binding mode, almost half a century ago, intense efforts have been devoted to design, synthesize and test new small molecules that can bind nucleic acids with improved recognition and affinity. Among them, metal bearing compounds play a principal role. Despite the plethora of different metal complexes which have been designed to react with DNA and which have been tested, the binding mechanisms have often not been analysed. This is unfortunate, considering the importance of understanding of the binding features in depth in order to optimise their biological effects. This review covers articles where an analysis of the kinetic aspects of the interaction between the target metal compound and nucleic acids has been carried out and details of the reaction mechanism are provided. Flat metal complexes (porphyrins), spherical complexes with protruding intercalating residues, azamacrocycle metallo-intercalators and intercalators with metal bearing pendant arms are the classes of molecules that have been taken into account. The limits of the SDS method, employed to measure the rates of drug dissociation from polynucleotides, are also discussed.