Efficient and Mild Microwave-Assisted Stepwise Functionalization of Naphthalenediimide with α-Amino Acids

Microwave dielectric heating proved to be an efficient method for the one-pot and stepwise syntheses of symmetrical and unsymmetrical naphthalenediimide derivatives of α-amino acids. Acid-labile side chain protecting groups are stable under the reaction conditions; protection of the α-carboxylic group is not required. The stepwise condensation of different amino acids resulted in high yields of unsymmetrical naphthalenediimides. The reaction proceeds without racemization and is essentially quantitative.

Subphthalocyanine-Stoppered [2]Rotaxanes:Synthesis and Size/Energy Threshold of Slippage

Subphthalocyanine (SubPc)-stoppered [2]rotaxanes were synthesized for the first time. The rotaxane bearing unsubstituted SubPc as a stopper exhibited an equilibrium of slipping-on and slipping-off, whereas a perfluorinated SubPc stopper completely blocked slippage of the ring due to its slightly larger size. Kinetic studies revealed the Gibbs free energy of activation for the slipping-on and slipping-off processes. The optical properties of the rotaxanes, including photoinduced electron transfer, were also revealed.</p

Chiral Phthalocyanines through Axial Coordination

A novel approach to axially induce chirality on silicon phthalocyanines via a microwave-assisted route is reported. CD analysis provides spectroscopic evidence that chirality is transferred onto both Soret and Q-bands of the phthalocyanine core. A chiral naphthalenediimide ligand was found to induce the largest Cotton effect on the macrocycle absorptions

Optical activity in third-harmonic Rayleigh scattering: A new route for measuring chirality

In 3D isotropic liquids, optical third-harmonic generation is forbidden, with circularly polarized light (CPL). Yet the associated nonlinear susceptibility directly influences the optical properties at the fundamental frequency by intensity dependence (Kerr effect). Here, the hidden third-harmonic optical properties upon CPL illumination are revealed by demonstrating a new effect, in hyper-Rayleigh scattering. This effect is succinctly enunciated: the intensity of light scattered at the third-harmonic frequency of the CPL incident light depends on the chirality of the scatterers. It is referred to as third-harmonic (hyper) Rayleigh scattering optical activity (THRS OA) and was observed from Ag nanohelices randomly dispersed in water. The first analytical theory model for the new effect in nanohelices is also provided, highlighting the role of localized transition dipoles along the helical length. THRS OA is remarkably user-friendly. It offers access to intricate optical properties (hyperpolarizabilities) that have so far been more easily accessible by computation and that are essential for the understanding of light−matter interactions. The new effect could find applications in hyper-sensitive characterization of the chirality in molecules and in nanostructures; this chirality plays a fundamental role in the function of bio/nano-machinery, with promising applications in next generation technologies

Thermally reduced graphene oxide nanohybrids of chiral functional naphthalenediimides for prostate cancer cells bioimaging

This study reports on the supramolecular assemblies formed between planar carbon systems (PCSs) such as thermally reduced graphene oxide (TRGO) and its small-molecule model system coronene and a series of d- and l-α amino acid derivatized naphthalenediimides (NDIs) where the halogen substituents (X = F, Cl, Br, I) are varied systematically. Confocal fluorescence microscopy of NDIs, NDI•coronene, and NDI•TRGO complexes is performed proving the uptake and stability of such complexes in the cellular environment and suggesting their potential as prostate cancer imaging agents. 1H NMR and UV-vis spectroscopy studies support the formation of charge transfer complexes whereby the increasing polarizability and general electronegativity of the aryl halide substituted at the NDI periphery influence the magnitude of the association constants in the ground state between NDI and coronene. Complexation between NDIs and PCSs also results in stable photoexcited assemblies within the solution (coronene) as well as the dispersed phased (TRGO). Fluorescence emission titrations and 2-photon time correlated single photon counting measurements suggest the existence of dynamic quenching mechanisms upon the excitation of the fluorophore in the presence of the carbon substrates, as these methods are sensitive proves for the subtle changes in the NDI environment. The series of halogenated species used exerts supramolecular control over the degree of surface assembly on the TRGO and over the interactions with the coronene molecule, and this is of relevance to the assembly of future biosensing platforms as these materials can both be viewed as congeners of graphene. Finally, MTT assays carried out in PC-3 cells demonstrate that the stable noncovalent functionalization of TRGO and coronene with either l or d NDIs remarkably improves the cellular viability in the presence of such graphene-like materials. These phenomena are of particular relevance for the understanding of the direct donor-acceptor interactions in solutions which govern the design of nanomaterials with future biosensing and bioimaging applications.</p

Labeling of graphene, graphene oxides, and of their congeners:imaging and biosensing applications of relevance to cancer theranostics

The area of biomedical imaging is fast becoming an active focus for the utilization of graphene within a variety of imaging modalities. Graphene can be oxidized to produce a material with a high degree of functionality and has led to its expansion as a platform for the immobilization of fluorescent and radiolabeled molecules. Its large surface area has allowed graphene and its oxides to be modified with a variety of molecules that enhance biocompatibility, selectivity, and therapeutic potential. This chapter highlights recent developments in the use of targeted fluorogenic or radiolabeled graphene materials that can be used to image cancers via fluorescence, positron emission tomography, and single-photon emission computed tomography modalities. Key emphasis is placed on the nanocomposites that are designed to provide additional therapeutic effects. The capacity of these composites to be internalized by cells and tumors is discussed to appreciate the future perspective of graphene and its congeners as therapeutic multimodal imaging agents.</p

Single- and double-helices of α,α′-dibenzylaminotripyrrin: solution and solid state studies

The dimeric association of α, α′-di(benzylamino)tripyrrin in chloroform was found to be 40 times less effective than that of previously reported α, α′-dianilinotripyrrin, which, however, led us to observe the co-crystal structure of single and double helix forms. Attachment of chiral phenylethylamines on the same tripyrrin platform was also performed to induce helical chirality