Several BrRe(CO)3L complexes (where L groups are 2,2'-biquinoline substituted in the 3 and 3' positions) were prepared. Their pseudooctahedralfuc structure was established by using FTIR, UV-vis, and 1H-NMR and confirmed by X-ray analysis. A good correlation between the electrochemical parameters and the MLCT electronic transition was found. The crystalline compound, BrRe(C0)3(3,3'-trimethylene-2,2'-biquinoline) belongs to triclinic space groupPiwitha=9,113(11)A,b= 10.192(4)A,c= 12.825(5)A,ar=73.23(4)0,B=81.30(7)0,andy=66.55(5)0.The volume of the unit cell is 1048(1) A3 with Z = 2. The structure was refined to R = 0.040.
The hydrodynamic interaction is an essential effect to consider in Brownian dynamics simulations of polymer and nanoparticle dilute solutions. Several mathematical approaches can be used to build Brownian dynamics algorithms with hydrodynamic interaction, the most common of them being the exact but time demanding Cholesky decomposition and the Chebyshev polynomial expansion. Recently, Geyer and Winter [J. Chem. Phys. 130, 1149051 (2009)] have proposed a new approximation to treat the hydrodynamic interaction that seems quite efficient and is increasingly used. So far, a systematic comparison among those approaches has not been clearly made. In this paper, several features and the efficiency of typical implementations of those approaches are evaluated by using bead-and-spring chain models. The different sensitivity to the bead overlap detected for the different implementations may be of interest to select the suitable algorithm for a given simulation.
We propose a multiscale protocol for the simulation of conformation and dynamics of dendrimer molecules in dilute solution. Conformational properties (radius of gyration, mass distribution, and scattering intensities) and overall hydrodynamic properties (translational diffusion and intrinsic viscosity) are predicted by means of a very simple coarse-grained bead-and-spring model, whose parameters are not adjusted against experimental properties, but rather they are obtained from previous, atomic-level simulations which are also quite simple, performed with small fragments and Langevin dynamics simulation. The scheme is described and applied systematically to four different dendrimer molecules with up to seven generations. The predictive capability of this scheme is tested by comparison with experimental data. It is found that the predicted geometric and hydrodynamic radii of the dendrimer molecules are in agreement (typical error is about 4%) with a large set experimental values of the four dendrimers with various numbers of generations. Agreement with some X-ray scattering experimental intensities also confirms the good prediction of the internal structure. This scheme is easily extendable to study more complex molecules (e.g., functionalized dendrimers) and to simulate internal dynamics.
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