Chemical studies on the nonlinear optics of coordination compounds

The exploration of molecule-based nonlinear optical (NLO) materials at the molecular level is one of the novel areas developed recently from the viewpoint of chemistry. This review summarizes some of our recent researcheson new NLO materials based on coordination compounds, which may have potential applications in optical devices.

Spectroscopic and electrochemical studies on molecular recognition of tetrathiafulvalene derivative with P-glycoprotein and drug-resistant leukemia cells

Cancer is still one of the important diseases that threatens the health of people. Multidrug resistance(MDR) is the main factor that leads to the failure of cancer chemotherapy. Thus, MDR diagnosis could facilitate the monitoring of the therapy process and realization of efficient treatment of tumors. In this study, we have tried to use a new tetrathiafulvalene(TTF) derivative(TTF-(COONBu4)2) to sensitively recognize the MDR through the multi-signal responsive strategy. The relevant electrochemical and spectroscopic studies demonstrate the specific binding behavior of TTF-(COONBu4)2 with P-glycoprotein(P-gp) as well as drug-resistant leukemia cells. Especially due to the over-expression of specific components of P-gp on the plasma membranes of drug resistant cells, the electrochemical and hydrophilic/hydrophobic features of drug resistant-leukemia cells are apparently different from those of other kinds of leukemia cells. Meanwhile, Fourier transform infrared spectroscopic study illustrates that the most intense vibration band of TTF moieties in the 1400–1600 cm-1 range is almost smeared out upon binding to P-gp, and the binding of TTF-(COONBu4)2 to P-gp may also lead to changes in protein secondary structure and backbone. This observation may advance the development of the new TTF agent for the promising clinical diagnosis and monitoring of MDR of tumors with the aim of successful chemotherapy for human cancer.

Cyanide-bridged single molecule magnet based on a manganese(Ⅲ) complex with TTF-fused Schiff base ligand

Reaction of [Mn（TTF-salphen）][OAc] （TTF-salphen2=2,2＇-（（2-（4,5-bis（methylthio）-1,3-dithiol-2-ylidene）-1,3-benzodithiole- 5,6-diyl）bis（nitrilomethylidyne）bis（pbenolate）dianion） and the cyanometalate building blocks [n-Bu4N][（Tp）Fe（CN）3] （Tp =Tris（pyrazolyl）hydroborate） or [n-Bu4N][Ru（salen）（CN）2] （salen2 =N,N＇-ethylenebis（salicylideneimine）dianion） resulted in the formation of two redox-active complexes, the dinuclear heterometallic complex [（Tp）Fe（CN）3Mn（TTF-salphen）＇CH3OH] （1） and the one dimensional complex [Ru（salen）（CN）2Mn（TTF-salphen）]n （2）. Both complexes were characterized by X-ray crystallography and solid state electrochemistry, in addition to static and dynamic magnetic measurements. Antiferromagnetic couplings are found to be operative between metal ion centers bridged by cyanide in both complexes. Complex 1 exhibited field-induced SMM behavior with an energy barrier of 13.8 K. The introduction of the redox-active TTF unit into cyanidebridged complexes with interesting magnetic properties renders them promising candidates for the construction of new hybrid inorganic-organic materials.

Highly Dynamic Polynuclear Metal Cluster Revealed in a Single Metallothionein Molecule

Human metallothionein(MT)is a small-size yet efficient metal-binding protein,playing an essential role in metal homeostasis and heavy metal detoxification.MT contains two domains,each forming a polynuclear metal cluster with an exquisite hexatomic ring structure.The apoprotein is intrinsically disordered,which may strongly influence the clusters and the metal-thiolate(M-S)bonds,leading to a highly dynamic structure.However,these features are challenging to identify due to the transient nature of these species.The individual signal from dynamic conformations with different states of the cluster and M-S bond will be averaged and blurred in classic ensemble measurement.To circumvent these problems,we combined a single-molecule approach and multiscale molecular simulations to investigate the rupture mechanism and chemical stability of the metal cluster by a single MT molecule,focusing on the Zn4S11 cluster in theαdomain upon unfolding.Unusual multiple unfolding pathways and intermediates are observed for both domains,corresponding to different combinations of M-S bond rupture.None of the pathways is clearly preferred suggesting that unfolding proceeds from the distribution of protein conformational substates with similar M-S bond strengths.Simulations indicate that the metal cluster may rearrange,forming and breaking metal-thiolate bonds even when MT is folded independently of large protein backbone reconfiguration.Thus,a highly dynamic polynuclear metal cluster with multiple conformational states is revealed in MT,responsible for the binding promiscuity and diverse cellular functions of this metal-carrier protein.