Tetraazaisoindigos:Serpentine Syntheses and Their Expected and Unexpected Photophysical and Electronic Properties.

Isoindigo, an electron-withdrawing building block for polymeric field-effect transistors, has long been considered to be non-fluorescent. Moreover, using electron-deficient heterocycle to replace the phenyl ring in the isoindigo core for better electron transport behaviour is synthetically challenging. Here we report the syntheses of a series of tetraazaisoindigos, including pyrazinoisoindigo (PyrII), pyrimidoisoindigo (PymII) and their hybrid (PyrPymII), and the investigation on their photophysical and electric properties. Proper flanking groups need to be chosen to stabilize these highly electron-deficient bislactams. Both PyrII and PymII derivatives show lower LUMO energy levels than that of naphthalene bisimide (NDI). Interestingly, PyrII is instinctively unstable and can be easily reduced, while both PymII derivatives are stable. More surprisingly, PymII derivatives are highly fluorescent and their photoluminescence quantum yields are around 40%, 133 times higher than that of reported isoindigo derivatives. UV-vis spectroscopic results and theoretical calculations show that strong intramolecular hydrogen-bond exists in PymII, which prohibits it from non-radiative decay and accounts for its fluorescent behaviour.  PymII deriviatives are n-type semiconductors, while Ph-PyrII and the hybrid show balanced ambipolar charge transport behaviour, all among the best isoindigo derivatives. Our study not only discloses the structure-property relationship of tetraazaisoindigos, but also provides electron-deficient monomers for conjugated polymers.

Platinum (IV) drugs with cannabidiol inducing mitochondrial dysfunction and synergistically enhancing anti-tumor effects.

Chemotherapy resistance is an insurmountable problem in clinical anticancer therapy. Although Oxaliplatin is an effective chemotherapeutic agent for the treatment of colorectal cancer (CRC), it still suffers from serious toxicities as well as drug resistance. In this work, three Oxaliplatin tetravalent platinum prodrugs(O1-O3) and three novel mixed ammine/amine analogs(C1-C3) were constructed, introducing cannabidiol with anti-tumor activity in their axial position. All Pt(IV) prodrugs exhibited potent antitumor effects in a variety of tumor cell lines, especially in HCT-116 cells, where complex O3 showed strong inhibitory effects with the half maximal inhibitory concentrations (IC50) value of 6.02 ± 0.69 µM and about 2.6 times higher than that of Oxaliplatin. Further studies revealed that complex O3 decreased cellular mitochondrial membrane potential in a concentration-dependent manner and enhanced reactive oxygen species (ROS) accumulation by decreasing the expression of catalase, superoxide dismutase 2 (SOD2) and superoxide dismutase 3 (SOD3). Complex O3 induces mitochondrial dysfunction and upregulates the pro-apoptotic protein Noxa, ultimately leading to severe DNA damage. The upregulation of Phosphorylated histone protein H2AX (γ-H2AX) expression is clear evidence. In addition, O3 inhibits the expression of RAD51 protein and prevents DNA damage repair, thus overcoming drug resistance. This strategy of combining bioactive molecules cannabidiol with platinum drugs to improve therapeutic efficacy and overcome drug resistance has been proven to be very effective and deserves further investigation.