Water-Induced Formation, Characterization, and Photoluminescence of Carbon Nanotube-Based Composites of Gadolinium(III) and Platinum(II) Dithiolenes

Understanding the nature of interactions of targeted drug-delivery vehicles, such as functionalized carbon nanotubes (f-CNTs) and their composites, with a cell or its organelles or DNA, where water is a major constituent, requires molecular-level understanding of f-CNTs with analogous chemical systems. The nature of interaction has not yet been explored within the scope of formation of giant aggregates by self-assembly processes. Crystals of platinum(II) dithiolene [Pt(mnt)(2)][PPh4](2) (1) and gadolinium(III) dithiolene [Gd(mnt)(3)][PPh4](3) (2) (mnt = maleonitrile dithiolate) form nanospheres (diameter 88 nm) and nanoflowers (400-600 nm) in acetonitrile/water and DMF/water solvent mixtures, respectively. The formation of nanospheres or nano-flowers is proposed to be a water-induced phenomenon. These nanospheres and nanoflowers interact with f-CNTs by forming either spherical supramolecular assemblies (3, diameter up to 45.5 mu m) in the case of platinum(II) dithiolene or composite flowers (4) with CNT buckling for gadolinium(III) dithiolene. Both nanostructures, (3) and (4), show emission upon excitation at a range of wavelengths (lambda(ex) = 385-560 nm). The fluorescence emissions of the composite materials 3 and 4 are proposed to be due to separation of energy states of the nanospheres of 1 or the nanoflowers of 2 by the energy states of the f-CNTs, leading to the possibility of new electronic transitions.