•Three alkynylplatinum(II) terpyridine complexes display high affinity for G-quadruplex.•The three complexes induce the formation of G-quadruplex in the absence of Na+ or K+.•The affinity of complexes for G-quadruplex decreases under molecular crowding condition.•The three complexes exhibit higher cytotoxicity against cancer cells than cisplatin.The interactions between alkynylplatinum(II) terpyridine complexes 1–3 and the G-quadruplex DNA, including c-myc and telomeric quadruplex DNA, are investigated both in dilute solution and under molecular crowding conditions. The UV–vis absorption spectroscopy, circular dichroism and molecular docking studies suggest that 1–3 associate with telomeric and c-myc G-quadruplexes via groove binding, and electrostatic interactions. Experimental studies indicate that under molecular crowding conditions (in the presence of 40 wt% PEG 200), 1–2 show weak affinity for c-myc, while 3 still displays high affinity and selectivity for c-myc. On the other hand, 1–3 act as efficient and selective ligand for telomeric quadruplex DNA under molecular crowding conditions. The complex 3 exhibits excellent cytotoxicity against A549, K562 and SGC-7901, with IC50 values that are 35.0-fold, 10.0-fold, and 12.1-fold lower than the values of cisplatin under the same conditions, respectively.The binding constants between three alkynylplatinum(II) terpyridine complexes and G-quadruplexes decrease significantly in the presence of crowding agent. One of the three complexes still shows high affinity (Ka > 106 M− 1) and selectivity for G-quadruplexes under molecular crowding conditions, and exhibits excellent cytotoxicity against cancer cell lines.

Four novel naphthalimide–thiourea conjugates 3a–d have been prepared and characterized. The interactions of these compounds with duplex and telomeric G-quadruplex DNA have been investigated by UV-Vis spectroscopy, fluorescence spectroscopy, viscosity and cyclic voltammetric measurements. The studies reveal that 3a–d possess high affinity (>1.20 × 107 M−1) and reasonable selectivity for telomeric G-quadruplex DNA over duplex DNA. Viscosity and cyclic voltammetric experiments suggest that 3a–d bind to duplex DNA through a classical intercalation mode. Molecular docking studies indicate that 3a–d associate with telomeric G-quadruplexes through groove binding, and hydrogen bonding interactions exist between the thiourea moiety and the phosphates or the bases in the G-quadruplex. The emissive nature of compounds 3a–d makes it possible to study their localization in A549 cells by fluorescence microscopy. The representative compounds 3d and 3b are mainly localized in the nuclei after 4 h of incubation. All four compounds inhibit A549 cells selectively over normal HUVEC cells, with a higher antitumor activity than amonafide.

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.