Intra- and intermolecular force field parameters for the interaction of actinyl ions (AnO2(n+), where, An = U, Np, Pu, Am and n = 1, 2) with water have been developed using quantum mechanical calculations. Water was modeled with the extended simple point charge potential (SPC/E). The resulting force field consists of a simple form in which intermolecular interactions are modeled with pairwise Lennard-Jones functions plus partial charge terms. Intramolecular bond stretching and angle bending are treated with harmonic functions. The new potentials were used to carry out extensive molecular dynamics simulations for each hydrated ion. Computed bond lengths, bond angles and coordination numbers agree well with known values and previous simulations. Hydration free energies, computed from molecular dynamics simulations as well as from quantum simulations with a solvation model, were in reasonable agreement with estimated experimental values.

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The reaction of [Cu(NCMe) 4 ] [PF 6 ] with aromatic acetylenes HC 2 R and triphosphine 1,1,1-tris-(diphenylphosphino)methane in the presence of NEt 3 results in the formation of hexanuclear Cu(I) clusters with the general formula [Cu 6 (C 2 R) 4 {(PPh 2 ) 3 CH} 2 ][PF 6 ] 2 (R = 4-X-C 6 H 4 (1−5) and C 5 H 4 N (6); X = NMe 2 (1), OMe (2), H (3), Ph (4), CF 3 (5)). The structural motif of the complexes studied consists of a Cu 6 metal core supported by two phosphine ligands and stabilized by σ-and π-coordination of the alkynyl fragments (together with coordination of pyridine nitrogen atoms in cluster 6). The solid state structures of complexes 2−6 were determined by single crystal XRD analysis. The structures of the complexes in solution were elucidated by 1 H, 31 P, 1 H− 1 H COSY NMR spectroscopy, and ESI mass spectrometry. Clusters 1−6 exhibit moderately strong phosphorescence in the solid state with quantum yields up to 17%. Complexes 1−5 were found to form solvates (acetone, acetonitrile) in the solid state. The coordination of loosely bound solvent molecules strongly affects emission characteristics and leads to solvato-and vapochromic behavior of the clusters. Thus, solventfree and acetonitrile solvated forms of 3 demonstrate contrasting emission in orange (615 nm) and blue (475 nm) regions, respectively. The computational studies show that alkynyl-centered IL transitions mixed with those of MLCT between the Cu 6 metal core and the ligand environment play a dominant role in the formation of excited states and can be considerably modulated by weakly coordinating solvent molecules leading to luminescence vapochromism. ■ INTRODUCTIONThe study of coinage metal complexes continues to consistently be one of the forefront areas of organometallic chemistry over the past three decades. A large variety of Cu, Ag, and Au species have found applications in catalysis and formed a basis for new functional materials with unusual physical characteristics. In particular, the attractive photophysical behavior of copper subgroup metal complexes, which includes highly efficient and tunable luminescence, significantly stimulates preparative efforts in the search for novel emissive objects. 1 An intrinsic feature of the closed-shell d 10 compounds (i.e., those of M I ions, M = Cu, Ag, Au) is a strong tendency to form extended networks of metallophilic bonds, which facilitate the assembly of multinuclear metal cores. 2 In addition to the fascinating structural diversity of these aggregates, reaching supramolecular and nanoscale levels, the metal−metal interactions are often responsible for a dramatic change or emergence of photoemission and nonlinear optical properties. 3 Moreover, a relative weakness of the metallophilic bonds (the strength of which is comparable to that of hydrogen bonding), 4 stands behind the easiness of their modulation and, consequently, sensitivity to certain external stimuli (chemical vapors, mechanical force, temperature). 1h,3e,f,h,5 The latter phenomena give rise to stimuli-responsive ma...

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