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 nanoflowers 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 μm) 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 (λex =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.