Two novel metal complexes 2–3 (metal = PdII, PtII) have been synthesized by reacting the corresponding tolylterpyridine complexes and the 4-aminonaphthalimide derivative 1. The interactions of the complexes with duplex DNA and telomeric G-quadruplex DNA have been investigated by UV-Vis spectroscopy and fluorescence spectroscopy. The studies reveal that the complexes 2–3 possess high affinity and reasonable selectivity for telomeric G-quadruplex DNA over duplex DNA. Spectroscopic and molecular docking studies suggest that the complexes 2–3 interact with telomeric G-quadruplex DNA mainly through groove binding. The compounds 1–3 are emissive (Φem > 0.22), making it possible to study the localization of 1–3 in A549 using fluorescence microscopy. The complexes 2–3 are mainly localized in nuclei, while 1 is localized in the nuclei and cytoplasmic region after 0.5 h incubation. The complex 3 inhibits A549 cells selectively over non-cancerous NIH3T3 cells, with higher antitumor activity than 1 and cisplatin.

Novel electron acceptors are synthesized through methylation of dipyrido[3,2-a:2′,3′-c]-7-aza-phenazine and dibenzo[a,c]-7-aza-phenazine. Absorption and fluorescence titration experimental results suggest that these phenazine derivatives may bind to aspartic acid modified perylene diimide (PASP) with moderate apparent association constant Ka (2.94 × 104 to 1.30 × 106 M−1). Solvent polarity, electron accepting ability and the phenazine derivative substituents all have an important effect on the binding strength of the PASP–phenazine complex. Photoinduced electron transfer from PASP to phenazine derivatives is confirmed by electrochemical, electron paramagnetic resonance (EPR) and time-resolved fluorescence experiments. The PASP–phenazine may form needle-like or rod-like nanostructures with lengths from 100 to 400 nm depending on their interaction model.

The yttrium coordination polymer of pyrene modified hypocrellin A (Y3+–PyrHA) is synthesized and characterized. The methoxydiglycol malonate modified fullerene can be included in the cavity of Y3+–PyrHA in organic solution and buffer solution containing amphiphilic polymers, such as polyvinyl pyrrolidone (PVP), pluronic F127 and P123. The interaction between an amphiphilic polymer and Y3+–PyrHA plays an important role in controlling the size and morphology of Y3+–PyrHA/fullerene. TEM images of Y3+–PyrHA/fullerene in 1% F127 and P123 show nanoparticles in the size range 10–60 nm, while TEM images of Y3+–PyrHA/fullerene in 1% PVP display large-scale aggregation. Singlet oxygen is generated by irradiation of the polymer solution of Y3+–PyrHA/fullerene in the presence of oxygen. The electron paramagnetic resonance (EPR) spin trapping and 9,10-dimethoxyanthracene-2-sulfonic acid sodium salt (MAS) photooxidation results suggest that in 1% P123 solution Y3+–PyrHA/fullerene exhibits a higher singlet oxygen quantum yield than Y3+–PyrHA and the corresponding fullerene.

The metal coordination polymer of hypocrellin A bearing tryptamine motif (M–DTrpHA) can include fullerene via a two-point interaction, involving π–π stacking and electron donor–acceptor interaction. The 1:1 host–guest system M–DTrpHA/fullerene exhibits a moderate association constant Ka (6.62 × 104 to 6.46 × 105 M–1). Both of the metal ions in M–DTrpHA and the substituents connected to the fullerene core play important roles in stabilizing the M–DTrpHA/fullerene complex. Transient absorption spectral and NIR absorption spectral results demonstrate that, in the M–DTrpHA/fullerene system, efficient photoinduced electron transfer from the tryptamine group in M–DTrpHA to fullerene may occur, resulting in a long-lived fullerene anion radical. The observed order of quantum yield (ΦETT) and rate constants (KETT) for electron transfer via 3C60* is Y3+–DTrpHA > La3+–DTrpHA > DTrpHA, consistent with their binding ability to C60. The nanostructure of M–DTrpHA is rearranged to form an interpenetrating network after interaction with fullerene.

Interaction of hypocrellin A (HA), a naturally perylenequinonoid, with fullerene C70 has been studied by UV–vis and fluorescence spectra, and the results show that HA and C70 can form a supramolecular assembly HA/C70 with a 2:1 stoichiometry in organic solvents and buffer solution containing poly(vinylpyrrolidone) (PVP). The triplet lifetime of HA and C70 are reduced due to the formation of supramolecular complex. Electron paramagnetic resonance (EPR) studies suggest that photoinduced electron transfer from N,N,N′N′-tetramethyldiethyleneamine (TMEDA) to the excited HA induces the generation of anion radical of HA (HA−), followed by further electron transfer from HA− to C70. HA can mediate the electron transfer from TMEDA to C70 and significantly enhance the intensity of characteristic Near-IR absorption transition of C70−, through efficient electron-transfer processes. Upon visible light irradiation, HA/C70 exhibits stronger photodamage ability on calf thymus DNA under anaerobic condition than HA and C70.

Riboflavin (RF), a metabolizable endogenous pigment, can significantly enhance the water solubility of naphthaleneacetate modified fullerene C60 (NP-C60) upon formation of a supramolecular complex (RF/NP-C60). NP-C60 can quench the fluorescence of RF efficiently through static quenching mechanism. The resulting complex exhibits strong affinity to calf thymus DNA, as indicated by the hypochromism of its absorption spectra. Under anaerobic conditions, RF/NP-C60 complex displays much more efficient photocleavage of the DNA than RF itself due to the occurrence of electron transfer from DNA to NP-C60.