Specific Design of Titanium(IV) Phenolato Chelates Yields Stable and Accessible,Effective and Selective Anticancer Agents

Octahedral titanium(IV) complexes of phenolato hexadentate ligands were developed and showed very high stability for days in water solutions. In vitro cytotoxicity studies showed that, whereas tetrakis(phenolato) systems are generally of low activity presumably due to inaccessibility, smaller bis(phenolato)bis(alkoxo) complexes feature high anticancer activity and accessibility even without formulations, also toward a cisplatin‐resistant cell line. An all‐aliphatic control complex was unstable and inactive. A leading phenolato complex also revealed: 1) high durability in fully aqueous solutions; accordingly, negligible loss of activity after preincubation for three days in medium or in serum; 2) maximal cellular accumulation and induction of apoptosis following 24–48 h of administration; 3) reduced impact on noncancerous fibroblast cells; 4) in vivo efficacy toward lymphoma cells in murine model; 5) high activity in NCI‐60 panel, with average GI₅₀ of 4.6±2 μm . This newly developed family of Ti^IV complexes is thus of great potential for anticancer therapy.     

Copper‐Catalyzed Amidation of Primary and Secondary Alkyl Boronic Esters

The oxidative copper‐catalyzed cross‐coupling of functionalized alkyl boronic esters with primary amides is reported. Through the identification of appropriate diketimine ligands, conditions for efficient coupling of both primary and secondary alkyl boronic esters with diverse primary amides, including acetamide, have been developed.     

Nitrogen Donor Protection for Atomically Precise Metal Nanoclusters

Surface organic ligands are critical in dictating the structures and properties of atomically precise metal nanoclusters. In contrast to the conventionally used thiolate, phosphine and alkynyl ligands, nitrogen donor ligands have not been used in the protection for well-defined metal nanoclusters until recently. This review focuses on recent developments in atomically precise metal nanoclusters stabilized by different types of nitrogen donor ligands, in which the synthesis, total structure determination and various properties are covered. We hope that this review will provide insights into the rational design of N donor-protected metal nanoclusters in terms of structural and functional modulation.     

Near-IR absorbing donor–acceptor charge-transfer gallium complex,an example from non-transition metal chemistry

Gallium(III) catecholates with bipyridine ligand [(3,5-Cat)Ga(bipy)2]I and (3,6-Cat)GaI(bipy) (Cat is di-tert-butylcatecholate) were synthesized and characterized by single-crystal X-ray diffraction. The appearance of near-infrared ligand-to-ligand charge transfer for pentacoordinate complex was observed.     

Chiral Ligands in Hypervalent Iodine Compounds: Synthesis and Structures of Binaphthyl-Based λ3-Iodanes

Several novel binaphthyl-based chiral hypervalent iodine(III) reagents have been prepared and structurally analysed. Various asymmetric oxidative reactions were applied to evaluate the reactivities and stereoselectivities of those reagents. Moderate to excellent yields were observed; however, very low stereoselectivities were obtained. NMR experiments indicated that these reagents are very easily hydrolysed in either chloroform or DMSO solvents leading to the limited stereoselectivities. It is concluded that the use of chiral ligands is an unsuccessful way to prepare efficient stereoselective iodine(III) reagents.     

Helicate tris(aryl)carbinolates bearing pendant NR2 donors – a new family of supporting ligands for the synthesis of Sc3+ alkyl complexes

The reactions of aryllithium reagents o-LiC₆H₄CH₂NR₂ with (MeO)₂CO afford two new tris(aryl)carbinols bearing pendant-NR₂ donor groups in the side chain [o-R NCH C H ] COH [R = Me, R + R = (CH) ]. These alcohols feature helical chirality due to differently inclined aromatic fragments and are presented in a crystalline cell as two M and P enantiomers. Carbinol (R = Me) readily reacts with (Me3SiCH2)3Sc(THF)2 to give a scandium bis(alkyl) complex [(o-C₆H₄CH₂NMe₂)₃CO]Sc(CH₂SiMe₃)₂ featuring rigid binding of the alkoxy anion through a κ¹-O, κ²-N chelating coordination mode     

Reentrant behavior of magnetic ordered phase in spin-crossover solids with quenched disordered ligand field

The Ising-like model of spin-crossover solid compounds with quenched random ligand field has been investigated by the mean-field (infinite-range) approximation. An exact solution for the problem is found within the replica formalism. The magnetic diagrams are obtained; the relations between the intermolecular coupling and the temperature as well as the reentrant phenomena of the magnetic ordered phase are discussed.     

Electronic Transitions in Different Redox States of Trinuclear 5,6,11,12,17,18-Hexaazatrinaphthylene-Bridged Titanium Complexes: Spectroelectrochemistry and Quantum Chemistry

Multinuclear transition metal complexes bridged by ligands with extended π-electronic systems show a variety of complex electronic transitions and electron transfer reactions. While a systematic understanding of the photochemistry and electrochemistry has been attained for binuclear complexes, much less is known about trinuclear complexes such as hexaphenyl-5,6,11,12,17,18-hexaazatrinaphthylene-tristitanocene [(Cp₂Ti)₃HATN(Ph)₆]. The voltammogram of [(Cp₂Ti)₃HATN(Ph)₆] shows six oxidation and three reduction waves. Solution spectra of [(Cp₂Ti)₃HATN(Ph)₆] and of the electrochemically formed oxidation products show electronic transitions in the UV, visible and the NIR ranges. Density functional theory (DFT) and linear response time-dependent DFT show that the three formally titanium(II) centers transfer an electron to the HATN ligand in the ground state. The optically excited transitions occur exclusively between ligand-centered orbitals. The charged titanium centers only provide an electrostatic frame to the extended π-electronic system. Complete active self-consistent field (CASSCF) calculation on a structurally simplified model compound, which considers the multi-reference character imposed by the three titanium centers, can provide an interpretation of the experimentally observed temperature-dependent magnetic behavior of the different redox states of the title compound in full consistency with the interpretation of the electronic spectra.