A tale of two modes: An end‐on copper superoxo complex was identified in a combined experimental and theoretical study. Theory clearly discloses the presence of an end‐on complex (see picture, O red, Cu pink, N green) with a minute isotopic resonance Raman splitting below experimental resolution. The results cast doubts on the uncritical use of 16O,18O isotopic‐labeling Raman experiments to discriminate end‐on from side‐on bonding modes in M(O2) complexes.

The photophysical properties of a series of Ru(II) complexes containing benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn) as a ligand are reported. Transient absorption spectroscopy studies indicate that, in contrast to related Ru(dppz) complexes (dppz = dipyrido[3,2-a:2',3'-c]phenazine), the excited state of all the dppn systems is a long-lived pipi* triplet state. Computational studies (DFT and TD-DFT) confirm that the excited state is based on the dppn ligand. Near-infrared luminescence studies reveal that the complexes are efficient singlet oxygen sensitizers with yields of 70-83%.

Rapid and regioselective activation of the C-F bond of 2,4,6-trifluoropyrimidine occurs on reaction with [Ni(cod)(2)] (cod=1,5-cyclooctadiene) in the presence of PEt(3) to give 1, which can be converted into complex 2, containing a further N(3)-metalated pyrimidin-4-one unit. The novel pyrimidin-4-one 3 is released on protonation of 2.

Three new ruthenium(II) complexes containing the tris(1-pyrazolyl)methane (tpm) ligand have been prepared: [Ru(tpm)(L)(dppn)]n+ (where n = 1; L = Cl (5), n = 2; L = MeCN (6) and pyridine (7); dppn = benzo[i]dipyrido[3,2-a:2',3'-c]phenazine). Complex 6 was structurally characterized by single-crystal X-ray diffraction. Binding parameters of these complexes with calf thymus DNA are reported and compared to those obtained for a previously reported monocation, [RuCl(tpm)(dppz)]+. Binding studies with the dications and the synthetic oligonucleotides poly(dA).poly(dT) and poly(dG).poly(dC) have also been determined. Photophysical and electrochemical properties of 5-7 have been investigated and compared with their dipyridophenazine (dppz) analogues.

In this article, we describe a series of complexes with electron-rich cis-{Ru II (NH 3 ) 4 } 2+ centers coordinated to two pyridyl ligands bearing N-methyl/arylpyridinium electron-acceptor groups. These V-shaped dipolar species are new, extended members of a class of chromophores first reported by us (Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 4845-4859). They have been isolated as their PF 6salts and characterized by using various techniques including 1 H NMR and electronic absorption spectroscopies and cyclic voltammetry. Reversible Ru III/II waves show that the new complexes are potentially redox-switchable chromophores. Single crystal X-ray structures have been obtained for four complex salts; three of these crystallize noncentrosymmetrically, but with the individual molecular dipoles aligned largely antiparallel. Very large molecular first hyperpolarizabilities β have been determined by using hyper-Rayleigh scattering (HRS) with an 800 nm laser and also via Stark (electroabsorption) spectroscopic studies on the intense, visible d f π* metal-to-ligand charge-transfer (MLCT) and π f π* intraligand charge-transfer (ILCT) bands. The latter measurements afford total nonresonant β 0 responses as high as ca. 600 × 10 -30 esu. These pseudo-C 2v chromophores show two substantial components of the β tensor, β zzz and β zyy , although the relative significance of these varies with the physical method applied. According to HRS, β zzz dominates in all cases, whereas the Stark analyses indicate that β zyy is dominant in the shorter chromophores, but β zzz and β zyy are similar for the extended species. In contrast, finite field calculations predict that β zyy is always the major component. Time-dependent density functional theory calculations predict increasing ILCT character for the nominally MLCT transitions and accompanying blue-shifts of the visible absorptions, as the ligand π-systems are extended. Such unusual behavior has also been observed with related 1D complexes (Coe, B. J. et al.