Cyclometalated Ir(III) theranostic molecular probe enabled mitochondria targeted fluorescence-SERS-guided phototherapy in breast cancer cells.

The increased energy demands inherent in cancer cells necessitate a dependence on mitochondrial assistance for their proliferation and metastatic activity. Herein, an innovative photo-medical approach has been attempted, specifically targeting mitochondria, the cellular powerhouses, to attain therapeutic benefit. This strategy facilitates the rapid and precise initiation of apoptosis, the programmed cell death process. In this goal, we have synthesized cyclometalated Iridium (III) molecular probes, denoted as Ir-CN and Ir-H, with a nitrile (CN) and a hydrogen-functionalized bipyridine as ancillary ligands, respectively. Ir-CN has shown superior photosensitizing properties and lower dark cytotoxicity compared to Ir-H in the breast cancer cell line MCF-7, positioning it as the preferred probe for photodynamic therapy (PDT). The synthesized Ir-CN induces alterations in mitochondrial membrane potential, disrupting the respiratory chain function, and generating reactive oxygen species that activate signaling pathways leading to cell death. The CN-conjugated bipyridine ligand in Ir-CN contributes to the intense red fluorescence and the positive charge on the central metal atom facilitates specific mitochondrial colocalization (colocalization coefficient of 0.90). Together with this, the Iridium metal, with strong spin-orbit coupling, efficiently generates singlet oxygen with a quantum yield of 0.79. Consequently, the cytotoxic singlet oxygen produced by Ir-CN upon laser exposure disrupts mitochondrial processes, arresting the electron transport chain and energy production, ultimately leading to programmed cell death. This mitochondrial imbalance and apoptotic induction were dually confirmed through various apoptotic assays including Annexin V staining and by mapping the molecular level changes through surface-enhanced Raman spectroscopy (SERS). Therefore, cyclometalated Ir-CN emerges as a promising molecular probe for cancer theranostics, inducing laser-assisted mitochondrial damage, as tracked through bimodal fluorescence and SERS.

Polycyclic Aromatic Hydrocarbons as Anode Materials in Lithium-Ion Batteries: A DFT Study.

The structure and energetics of the interactive behavior of Li+ and Li with polycyclic aromatic hydrocarbons (PAHs) have been studied at the wB97XD/6-311G(d,p) level of DFT. The electron distribution in the PAHs, analyzed using the topology of the molecular electrostatic potential (MESP), led to the categorization of their aromatic rings into five types, viz Rs, Rn, Rd, Rb, and Re. Among the different rings, sextet-type Rs and naphthalene-type Rn rings showed the highest interaction with Li+. The change in MESP at the nucleus of Li+ (ΔVLi+) due to the formation of the complex Li+...PAH is found to be proportional to the adsorption energy (E1). In Li...PAH, the spin density on Li is close to zero, suggesting the formation of Li+...PAH•- due to the electron transfer from Li to PAH. The adsorption energy (E2) for Li...PAH does not correlate with the change in MESP at the nucleus of Li, whereas the dissociation energy (E3) of Li+...PAH•- to yield Li+ and PAH•- correlates well with the MESP data, ΔVLi. The study confirms that the change in MESP at the nucleus of Li+ due to complex formation gives a quantitative measure of the electronic effect of the cation-π binding. The cell potential (Vcell) is predicted for the lithium ion battery (LIB) using the Li+...PAH and Li...PAH adsorption energies. On the basis of the Vcell data, "carbon nanoflake"-type systems, viz coronene, circumbiphenyl, C42H16, and C50H18 are suggested as good anode materials for LIBs.