Organometallic iridium complexes with two cyclometalated ligands (ĈN) and one bis-oxazoline derived ancillary ligand (L^X), . (ĈN)Ir(L^X), are reported. The ĈN ligands are 1-phenylpyrazoline (ppz), 2-(4,6-difluorophenyl)pyridine (Fppy), 2-phenylpyridine (ppy), 1-phenylisoquinoline (piq). The box ligand is (4S)-(+)-phenyl-α-[(4S)-phenyloxazolidin-2-ylidene]-2-oxazoline-2-acetonitrile. The emission of these complexes span across the visible and into the near-ultraviolet region of the electromagnetic spectrum with moderate to high photoluminescence quantum yields (Φ = 0.45-1.0). These complexes were found to emit from a metal-ligand to ligand charge transfer (ML'LCT) state and have lifetimes (1.3-2.1 μs), radiative rates (10 s), and nonradiative rates (10-10 s) comparable to state-of-the-art iridium emitters. The (ppy)Ir(BOX-CN) complexes were resolved into the Δ- and Λ- diastereomers using differences in their solubility and additionally characterized by x-ray crystallography, stability, and chiroptic studies. The high Φ of these isomers results in the best to date brightness for circularly polarized luminescence (CPL) from iridium complexes (7.0 M cm), with dissymmetry factors of -0.57 × 10 and +1.9 × 10 for and , respectively. The significant difference in CPL magnitude between and likely arises from interligand interactions (edge-to-face arrangement versus strong π-π interaction) for the pendant phenyl ring of the BOX-CN ligand which differ for the two isomers.

The bis(pyridylimino)isoindoline (BPI) ligand is a tridentate chelate that binds to metals via a meridional coordination mode. However, when this ligand forms a complex with Re(CO), an almost exclusively facial moiety, the BPI ligand deforms to coordinate in a facial mode. We have in-vestigated this deformation via structural and theoretical means, and the non-planar binding mode of the ligand bathochromically shifts the metal to ligand charge transfer (MLCT) transition.

Tricarbonylrhenium(I)(α-diimine) complexes are of importance because of their strong cytotoxic and fluorescence properties. Syntheses of such complexes were achieved through a two-step process. First, the pentylcarbonato complexes, -(CO)(α-diimine)ReOC(O)OCH were synthesized through a microwave-assisted reaction of Re(CO), α-diimine, 1-pentanol and CO in a few hours. Second, the pentylcarbonato complexes are treated with carboxylic, sulfonic and halo acids to obtain the corresponding carboxylato, sulfonato and halido complexes. This is the first example of conversion of Re(CO) into a rhenium carbonyl complex through microwave-assisted reaction.

[Cp*Rh] complexes (Cp* = -pentamethylcyclopentadienyl) supported by bidentate chelating ligands are useful in studies of redox chemistry and catalysis, but little information is available for derivatives bearing "hybrid" [] chelates. Here, the preparation, structural characterization, and chemical and electrochemical properties of a [Cp*Rh] complex bearing the κ-[,]-2-[(diphenylphosphino)methyl]pyridine ligand (PN) are reported. Cyclic voltammetry data reveal that [Cp*Rh(PN)Cl]PF () undergoes a chemically reversible, net two-electron reduction at -1.28 V vs. ferrocenium/ferrocene, resulting in generation of a rhodium(I) complex () that is stable on the timescale of the voltammetry. However, H and P{H} NMR studies reveal that chemical reduction of generates a mixture of products over a 1 h timescale; this mixture forms as a result of deprotonation of the methylene group of by followed by further reactivity. The analogous complex [Cp*Rh(PQN)Cl]PF (; PQN = κ-[,]-8-(diphenylphosphino)quinoline) does not undergo self-deprotonation or further reactivity upon two-electron reduction, confirming the reactivity of the acidic backbone methylene C-H bonds in the PN complexes. Comparison of the electrochemical properties and also shows that the extended conjugated system of PQN contributes to an additional ligand-centered redox event for that is absent for .

In this report, we present a study on the synthesis, structure, and electronics of a series of (8-amino)quinoline and (4-amino)phenanthridine complexes of Re(CO)X, where X = Cl and Br. In all cases, the (amino)heterocycles bind as bidentate ligands, with surprisingly symmetric modes of binding based on Re-N bond lengths. Between the complexes of (8-amino)quinolines and (4-amino)phenanthridines studied in this report, we do not observe much structural variation, and remarkably similar UV-visible absorption spectra. Expansion of the π-system in the (4-amino)phenanthridine complexes does result in an increase in the intensity of the lowest energy transitions (λ), which computational modeling suggests are more purely MLCT in character compared with the mixed π-π*/MLCT character of these transitions in the smaller (8-amino)quinoline-supported complexes. DFT and TDDFT modeling further showed that consideration of spin-orbit coupling (SOC) is essential; omitting SOC misses the π-π* contributions to λ and is unable to accurately model the observed electronic absorption spectra.

Methoxy and -butyl substituted carboxamide, carboxylic acid and hydrazone Schiff base groups have been assembled into our newly designed fluorenone based ligands and prepared coordination compounds of some first row transition metals and characterized thoroughly with spectroscopic (H and C NMR, IR, GC-MS, UV-Vis), analytical, TGA and molar conductance measurements. The stoichiometry of all the metal complexes is found to be 1: 2 (M: L) with the general formula, [M(L)], where L is a singly deprotonated ligand and the geometry of all the metal complexes is found to be octahedral. Ligands and their metal complexes successfully cleaved the pBR322 plasmid DNA and in case of anticancer activity against MCF-7 (human breast adenocarcinoma) cell line, the synthesized compounds found to exhibit excellent activity with prominent apoptotic effect which is characterized by cell shrinkage, cell breakage and turgidity and results were compared with the standard drug cisplatin. Very significant anticancer activity was observed for compounds LH, Cu(L), Cu(L), Ni(L) and Ni(L) with IC value of <10 μgmL. Molecular docking studies were performed to assess the bonding mode of synthesized compounds. In case of antioxidant activity study, the compounds LH, Ni(L), Ni(L), Cu(L) and Cu(L) exhibited significant scavenging activity with good percentage when compared with remaining tested compounds.

This report presents the synthesis and characterization of mono- and bis(amino acid ester) ferrocene complexes generated using a sulfonamide linking strategy as an alternative to the more heavily explored amide linking strategy. These compounds were investigated to test their ability to form hydrogen bonding interactions both in the solid state and in solution, and were compared to the previously observed intramolecular interstrand crosslinking seen in amide-linked ferrocene constructs. Synthesized compounds also included controls that do not exhibit sulfonamide N-H bonds and thus cannot engage in hydrogen bonding. In the solid state, we observe both S=O⋯H-N and C=O⋯H-N intermolecular interactions, but we do not observe any intramolecular interstrand hydrogen bonding. In the solution phase, we also do not see any intramolecular hydrogen bonding interactions in these compounds as measured by titration of d-DMSO as a competitive hydrogen bonding reagent. We also collected CD spectra on these compounds, which revealed that the chiral peptides can induce dichroism in the dd transition of the ferrocene units. Our results indicate that the peptide-ferrocene linking group governs whether intermolecular hydrogen bonding interactions can occur between the amino acids adjacent to the cyclopentadienyl groups.

The synthesis, structure and photophysical properties of the complexes [Ru[(CO)(TFA) (PPh)(L)] [(L = ppy = 2-phenylpyridine, (); L = 2-(p-tolyl)pyridine] (), are reported. The complexes were characterized by UV-VIS, IR and NMR and by single-crystal X-ray diffraction techniques. We also report the synthesis, structure and photophysical properties of [Ru(CO)(L)(PPhMe)(L')][PF]- [L' = bipyridine, L = TFA, (); L = H, () and L = H, L' = 4,4'-dimethlyl bipyridine ()]. These compounds were characterized by UV-VIS, IR and NMR techniques and by a single crystal X-ray diffraction in the case of . The solid state structure of [Ru(MePhP)(CO)(TFA) () which is the starting material for the synthesis - is also reported to verify the relationship of the less bulky PPhMe and for comparison with the previously reported PPh analogs. The purpose of this study was to determine the impact, if any, of replacing bpy with ppy in the case of and alkylation of the benzene ring in the case of on the photophysical and electrochemical properties compared to related Ru(bpy) complexes. In contrast to the bpy analogs and showed reversible 1e oxidations and blue-shifted MLCT absorptions. In the case of - we were interested in the effect on the photophysical properties of substituting PPh with the less bulky but more electron donating PPhMe. There were only minor changes in the photophysical and electrochemical properties relative to the previously reported PPh analogs.

Acetyl ferrocene and diacetyl ferrocene both readily react with an excess of hydrazine to afford the corresponding hydrazone compounds. These compounds can then be linked to Re(CO) via a metal-mediated Schiff base reaction, resulting in a series of ferrocene-Re(CO) conjugates with different stoichiometries. Conjugates with 1:1, 1:2, and 2:1 ferrocene: Re(CO) ratios can be produced via this "modular" type synthesis approach. Several examples of these conjugates were structurally characterized, and their spectroscopic, electrochemical, and spectroelectrochemical behaviors were investigated. The electronic structures of these compounds were also probed using DFT and TDDFT calculations.

A series of four BODIPYs containing one or two - or -carborane clusters were synthesized using palladium(0)-catalyzed Suzuki cross-coupling or nucleophilic substitution reactions, at the 2,6- or the 8-positions of halogenated boron dipyrromethenes (BODIPYs). The spectroscopic, structural (including one X-ray) and BBB permeability of the BODIPYs using hCMEC/D3 brain endothelial cells were investigated.

The (2-mercaptoimidazolyl)hydroborato ligand, [Tm ], has been used to investigate the exchange of alkyl and sulfur donor ligands between the Group 12 metals, Zn, Cd and Hg. For example, [Tm ]Zn reacts with MeZn to yield [Tm ]ZnMe, while [Tm ]CdMe is obtained readily upon reaction of [Tm ]Cd with MeCd. Ligand exchange is also observed between different metal centers. For example, [Tm ]CdMe reacts with MeZn to afford [Tm ]ZnMe and MeCd. Likewise, [Tm ]HgMe reacts with MeZn to afford [Tm ]ZnMe and MeHg. However, whereas the [Tm ] ligand transfers from mercury to zinc in the methyl system, [Tm ]HgMe/MeZn, transfer of the [Tm ] ligand from zinc to mercury is observed upon treatment of [Tm ]Zn with HgI to afford [Tm ]HgI and [Tm ]ZnI. These observations demonstrate that the phenomenological preference for the [Tm ] ligand to bind one metal rather than another is strongly influenced by the nature of the co-ligands.

Palladium-catalyzed methods for C-H oxygenation with O as the stoichiometric oxidant are limited. Here, we describe the use of nitrite and nitrate sources as NO-based redox mediators in the acetoxylation of benzene. The conditions completely avoid formation of biphenyl as a side product, and strongly favor formation of phenyl acetate over nitrobenzene (PhOAc:PhNO ratios up to 40:1). Under the optimized reaction conditions, with 0.1 mol% Pd(OAc), 136 turnovers of Pd are achieved with only 1 atm of O pressure.

Anthranilic acid (ANA) and 3-hydroxyanthranilic acid (3-HANA) are kynurenine pathway intermediates of the tryptophan metabolism. A hitherto unemployed method combination, differential pulse voltammetry, mass spectrometry (nano-ESI-MS), deoxyribose degradation and iron(II) autoxidation assays has been employed for studying of their redox chemistry and their interactions with iron(II) and iron(III) ions. Both acids inhibited the Fenton reaction by iron chelation and ROS scavenging in the deoxyribose degradation assay. In the iron(II) autoxidation assay, anthranilic acid showed antioxidant effects, whereas 3-hydroxyanthranilic acid exhibited apparent pro-oxidant activity. The differential pulse voltammograms of free metabolites and their iron(II) coordination complexes reflected these properties. Nano-ESI-MS confirmed ANA and 3-HANA as efficient iron(II) chelators, both of which form coordination complexes of ligand:iron(II) ratio 1:1, 2:1, and 3:1. In addition, nano-ESI-MS analyses of the oxidation effects by hydroxyl radical attack identified 3-HANA as strikingly more susceptible than ANA. 3-HANA susceptibility to oxidation may explain its decreased concentrations in the reaction mixture. The presented observations can add to explaining why 3-HANA levels decrease in patients with some neurological and other diseases which can often associated with elevated concentrations of ROS.

The tryptophan metabolite, quinolinic (2,3-pyridinedicarboxylic) acid, is known as an endogenous neurotoxin. Quinolinic acid can form coordination complexes with iron or copper. The effects of quinolinic acid on reactive oxygen species production in the presence of iron or copper were explored by a combination of chemical assays, classical site-specific and ascorbic acid-free variants of the deoxyribose degradation assay, and mass spectrometry (ESI-MS). Quinolinic acid showed evident antioxidant activity in chemical assays, but the effect was more pronounced in the presence of copper as transition metal catalyst than in presence of iron. Nano-ESI-MS confirmed the ability of quinolinic acid to form coordination complexes with iron(II) or copper(II) and quinolinic acid stability against oxidative attack by hydroxyl radicals. The results illustrate a highly milieu-dependent quinolinic acid chemistry when it enters reactions as competitive ligand.

A series of bis-phosphinite and bis-phosphite PONOP iron complexes were prepared and characterized by NMR and IR spectroscopy. Bis-phosphinite PONOP iron dichloride complexes (PONOP)FeCl (PONOP = 2,6-(RPO)(CHN) and R = Pr, Bu) were prepared through complexation of the free ligands with FeCl and their solid-state structures were determined. Bis-phosphite PONOP iron complexes (PONOP)Fe(PMe) and (PONOP)Fe(PMe) (Cat = catechol) were synthesized through complexation of the free ligands to Fe(PMe). Carbonyl complexes of both bis-phosphinite and bis-phosphite PONOP were prepared and characterized by IR. The monocarbonyl (PONOP)Fe(CO)Cl was accessed through exposure of (PONOP)FeCl to an atmosphere of CO and the CO stretching frequency was observed at 1969 cm. Dicarbonyl complexes (PONOP)Fe(CO) and (PONOP)Fe(CO) were accessed through reduction of the corresponding chloride complexes with sodium amalgam under a CO atmosphere. Carbonyl stretching frequencies for (PONOP)Fe(CO) and (PONOPFe)(CO) were observed at 1824 and 1876 cm, and at 1871 and 1927 cm respectively. The bis-phosphite PONOP complexes exhibit a less electron rich metal center than the bis-phosphinite PONOP complexes, as would be expected based on the stronger π-acceptor character of these ligands. The electronic properties of the bis-phosphinite PONOP and bis-phosphite PONOP iron complexes are intermediate between previously reported PNP and PDI iron complexes, with the PONOP ligands exhibiting stronger electron donating ability than PDI ligands, but promoting a less electron rich metal center than found in analogous PNP iron complexes.

Inductive perturbations of C-C triple bonds are shown to dictate the regiochemistry of gold-catalyzed oxidation of internal C-C triple bonds in the cases of propargylic ethers, resulting in highly regioselective formation of β-alkoxy-α,β-unsaturated ketones (up to >50/1 selectivity) via α-oxo gold carbene intermediates. Ethers derived from primary propargylic alcohols can be reliably transformed in good yields, and various functional groups are tolerated. With substrates derived from secondary propargylic alcohols, the development of a new ,-bidentate ligand enables the minimization of competing alkyl group migration to the gold carbene center over the desired hydride migration; the preferred migration of a phenyl group, however, results in efficient formation of a α-phenyl-β-alkoxy-α,β-unsaturated ketone. These results further advance the surrogacy of a propargyl moiety to synthetically versatile enone function with reliable and readily predictable regioselectivity.

In the present study a complete series of seven-coordinate neutral halocarbonyl Mo(II) complexes of the type [Mo(PNP-Ph)(CO)X] (X = I, Br, Cl, F), featuring the new PNP pincer ligand ,'-bis(diphenylphosphino)-,'-methyl-2,6-diaminopyridine (PNP-Ph), were prepared and fully characterized. The synthesis of these complexes was accomplished by different methodologies depending on the halide ligands. For X = I and Br, [Mo(PNP-Ph)(CO)I] and [Mo(PNP-Ph)(CO)Br] were obtained by reacting [Mo(PNP-Ph)(CO)] with stoichiometric amounts of I and Br, respectively. Alternatively, these complexes were obtained upon treatment of [MoX(CO)(CHCN)] (X = I, Br) with 1 equiv. of PNP-Ph. On the other hand, in the case of X = Cl, [Mo(PNP-Ph)(CO)Cl] was afforded by the reaction of [Mo(CO)(μ-Cl)Cl] with 1 equiv. of PNP-Ph. The equivalent procedure also worked for X = Br. Finally, addition of 1 equiv. of 1-fluoro-2,4,6-trimethylpyridinium tetrafluoroborate to [Mo(PNP-Ph)(CO)] yielded the analogous fluorine complex [Mo(PNP-Ph)(CO)F]. The modification of the ligand scaffold by introducing a Me group instead of H changed the properties of the PNP-Ph ligand significantly. While in the present case exclusively neutral seven-coordinate complexes of the type [Mo(PNP-Ph)(CO)X] were obtained, with the parent PNP-Ph ligand, i.e., featuring NH spacers, cationic seven-coordinate complexes of the type [Mo(PNP-Ph)(CO)X]X were afforded. DFT calculations indicated that the reactions are under thermodynamic control. The structures of representative complexes were determined by X-ray single crystal analyses.

Six ferrocenecarboxylates with phenyl, 4-(1-pyrrol-1-yl)phenyl, 4-fluorophenyl, 4-chlorophenyl, 4-bromophenyl, 4-iodophenyl as pendant groups were synthesized and fully characterized by spectroscopic, electrochemical and X-ray diffraction methods. The anti-proliferative activity of these complexes were investigated in hormone dependent MCF-7 breast cancer and MCF-10A normal breast cell lines, to determine the role of the para substituent on the phenoxy pendant group. The 4-fluorophenyl ferrocenecarboxylate is inactive in both cell lines while 4-(1-pyrrol-1-yl)phenyl ferrocenecarboxylate is highly cytotoxic in both cell lines. 4-chlorophenyl and 4-bromophenyl ferrocenecarboxylates have moderate to good anti-proliferative activity in MCF-7 and low anti-proliferative activity on normal breast cell line, MCF-10A whereas the 4-iodophenyl analog is highly toxic on normal breast cell line. The phenyl ferrocenecarboxylate has proliferative effects on MCF-7 and is inactive in MCF-10A. Docking studies between the complexes and the alpha-estrogen receptor (ER) were performed to search for key interactions which may explain the anti-proliferative activity of 4-bromophenyl ferrocenecarboxylate. Docking studies suggest the anti-proliferative activity of these ferrocenecarboxylates is attributed to the cytotoxic effects of the ferrocene group and not to anti-estrogenic effects.

Treatment of [FeCp(CO)Cl] with 1 equiv of the amidophosphine ligands Li[RPNR'] (R = Ph, Pr, R' = Pr, Bu, Cy) afforded complexes of the type [FeCp(CO)(κ(,)-(C = O)-NPr-PPh)] (), [FeCp(CO)(κ(,)-(C = O)-NBu-PPh)] (), and [FeCp(CO)(κ(,)-(C = O)-NCy-PPr)] () in 40-50% yields. Complex was also formed when [FeCp(CO)(PPhNHPr)] () was reacted with 1 equiv of KOBu. These complexes feature a four-membered carboxamido-phospha-ferracycle as a result of an intramolecular nucleophilic attack of the amidophosphine ligand on coordinated CO. Upon treatment of with the electrophile [MeO]BF the aminocarbene complex [FeCp(CO)((,) = C(OMe)-NPr-PPh)] () was obtained bearing an aza-phospha-carbene moiety. Upon treatment of ,,-[Fe(CO)(PhPNHPr)(Br)] () and ,,-[Fe(CO)(PhPNHBu)(Br)] () with KOBu the carboxamido-phospha-ferracycles -[Fe(CO)(κ(,)-(C = O)-NPr-PPh)(PhPNHPr)Br] () and -[Fe(CO)(κ(,)-(C = O)-NBu-PPh)(PhPNHBu)Br] () were formed in moderate yield. Finally, representative structures were determined by X-ray crystallography.

The new pyridine-2-carboxaldehyde adduct, Re(CO)(NCHC(O)H)Cl and previously reported complex Re(CO)(NCHC(O)H)Br react with aniline derivatives sulfanilamide or 4-aminofluorescein in methanol giving Schiff base conjugates Re(CO)(pyca-R)X (pyca = pyridinecarbaldehyde imine, X = Cl, Br), -. Pre-isolation of compounds and provides a convenient method for preparing conjugate complexes in addition to the known methods of ligand synthesis and one-pot reactions. All new compounds were completely characterized, and compound and the sulfanilamide derivatives and were structurally elucidated by X-ray crystallography.