Half-sandwich Os-arene complexes exhibit promising anticancer activity, but their photochemistry has hardly been explored. To exploit the photocytotoxicity and photochemistry of Os-arenes, O,O-chelated complexes [Os(η 6 -p-cymene)(Curc)Cl] (OsCUR-1, Curc = curcumin) and [Os(η 6 -biphenyl)(Curc)Cl] (OsCUR-2), and N,N-chelated complexes [Os(η 6 -biphenyl)(dpq)-I]PF 6 (OsDPQ-2, dpq = pyrazino[2,3-f ][1,10]phenanthroline) and [Os(η 6 -biphenyl)(bpy)I]PF 6 (OsBPY-2, bpy = 2,2′-bipyridine), have been investigated. The Os-arene curcumin complexes showed remarkable photocytotoxicity toward a range of cancer cell lines (blue light IC 50 : 2.6−5.8 μM, photocytotoxicity index PI = 23−34), especially toward cisplatin-resistant cancer cells, but were nontoxic to normal cells. They localized mainly in mitochondria in the dark but translocated to the nucleus upon photoirradiation, generating DNA and mitochondrial damage, which might contribute toward overcoming cisplatin resistance. Mitochondrial damage, apoptosis, ROS generation, DNA damage, angiogenesis inhibition, and colony formation were observed when A549 lung cancer cells were treated with OsCUR-2. The photochemistry of these Osarene complexes was investigated by a combination of NMR, HPLC-MS, high energy resolution fluorescence detected (HERFD), Xray adsorption near edge structure (XANES) spectroscopy, total fluorescence yield (TFY) XANES spectra, and theoretical computation. Selective photodissociation of the arene ligand and oxidation of Os(II) to Os(III) occurred under blue light or UVA excitation. This new approach to the design of novel Os-arene complexes as phototherapeutic agents suggests that the novel curcumin complex OsCUR-2, in particular, is a potential candidate for further development as a photosensitizer for anticancer photoactivated chemotherapy (PACT).

Photoactivatable agents offer the prospect of highly selective cancer therapy with low side effects and novel mechanisms of action that can combat current drug resistance. 1,8-Naphthalimides with their extended π system can behave as light-harvesting groups, fluorescent probes and DNA intercalators. We conjugated N-(carboxymethyl)-1,8naphthalimide (gly-R-Nap) with an R substituent on the naphthyl group to photoactive diazido Pt IV complexes to form t,t,t-[Pt(py) 2 (N 3 ) 2 (OH)(gly-R-Nap)], R = H (1), 3-NO 2 (2) or 4-NMe 2 (3). They show enhanced photo-oxidation, cellular accumulation and promising photo-cytotoxicity in human A2780 ovarian, A549 lung and PC3 prostate cancer cells with visible light activation, and low dark cytotoxicity. Complexes 1 and 2 exhibit pre-intercalation into DNA, resulting in enhanced photo-induced DNA crosslinking. Complex 3 has a red-shifted absorption band at 450 nm, allowing photoactivation and photo-cytotoxicity with green light.

We characterize NO A2S+ + O2 X3S  g Van der Waals (VdW) Potential Energy Surface (PES) with RHF/RCCSD(T) and CASSCF/CASPT2 calculations. To do this, we first assess our computational setup to...

The quenching of \noa with \oo as a collisional partner is important for combustion and atmospheric processes. There is still a lack of theoretical understanding of this event, especially concerning the nature of the different quenching pathways. In this work we provide potential energy surfaces (PESs) of 20 electronic states of this system. We computed the spin-doublet and spin-quartet PESs using SA-CASSCF and XMS-CASPT2. We find two potential quenching pathways. The first one (\textbf{$Q_{1}$}) is a 2-step orientation-specific process. The system first undergo an electron transfer (\nop + \oom) at short distances, before crossing to lower neutral states, such as \nox + \ooa, \oob, \oox or even 2 O($^{3}$P). The second quenching pathway (\textbf{$Q_{2}$}) is less orientation-dependent, and should be sudden without requiring the proximity conditioning \textbf{$Q_{1}$}. The \textbf{$Q_{2}$} cross-section will be enhanced with increasing initial vibrational level in both \oo and NO. It is responsible for the production of \nox with higher \oo excited states, such as \ooc, A$^{\prime}\ ^{3}\Delta_{u}\ $, or A $^{3}\Sigma^{+}_{u}\ $. Overall, this work provides a first detailed theoretical investigation of the quenching of \noa by \oox, as well as introducing a weighting scheme generally applicable to multireference, open-shell bimolecular systems. The effect of the spin-multiplicity on the different quenching pathways is also discussed.

A crossed molecular beam, velocity-map ion-imaging apparatus has been used to determine differential cross sections (DCSs), as a function of collider final internal energy, for rotationally inelastic scattering of NO(A2Σ+, v = 0, j = 0.5f 1) with N2, CO, and O2, at average collision energies close to 800 cm–1. DCSs are strongly forward scattered for all three colliders for all observed NO(A) final rotational states, N′. For collisions with N2 and CO, the fraction of NO(A) that is scattered sideways and backward increases with increasing N′, as does the internal rotational excitation of the colliders, with N2 having the highest internal excitation. In contrast, the DCSs for collisions with O2 are essentially only forward scattered, with little rotational excitation of the O2. The sideways and backward scattering expected from low-impact-parameter collisions, and the rotational excitation expected from the orientational dependence of published van der Waals potential energy surfaces (PESs), are absent in the observed NO(A) + O2 results. This is consistent with the removal of these short-range scattering trajectories via facile electronic quenching of NO(A) by O2, in agreement with the literature determination of the coupled NO-O2 PESs and the associated conical intersections. In contrast, collisions at high-impact parameter that predominately sample the attractive van der Waals minimum do not experience quenching and are inelastically forward scattered with low rotational excitation.