An efficient one-pot synthesis of carbazole fused benzoquinolines and pyridocarbazoles

Cobalt­(II), in the presence of acetate and nitrate, quantitatively adds to the manganese–cobalt oxido cubane Mn^IVCo^III₃O₄(OAc)₅(py)₃ (<b>1</b>) to furnish the pentametallic dangler complex Mn^IVCo^III₃Co^IIO₄(OAc)₆(NO₃)­(py)₃ (<b>2</b>). Complex <b>2</b> is structurally reminiscent of photosystem II’s oxygen-evolving center, and is a rare example of a transition-metal “dangler” complex. Superconducting quantum interference device magnetometry and density functional theory calculations characterize <b>2</b> as having an <i>S</i> = 0 ground state arising from antiferromagnetic coupling between the Co^II and Mn^IV ions. At higher temperatures, an uncoupled state dominates. The voltammogram of <b>2</b> has four electrochemical events, two more than that of its parent cubane <b>1</b>, suggesting that addition of the dangler increases available redox states. Structural, electrochemical, and magnetic comparisons of complexes <b>1</b> and <b>2</b> allow a better understanding of the dangler’s influence on a cubane

Synthesis and O2 Reactivity of a Titanium(III) Metal-Organic Framework.

Metal-organic frameworks featuring pores lined with exposed metal cations have received attention for a wide range of adsorption-related applications. While many frameworks with coordinatively unsaturated M(II) centers have been reported, there are relatively few examples of porous materials with coordinatively unsaturated M(III) centers. Here, we report the synthesis and characterization of Ti3O(OEt)(bdc)3(solv)2 (Ti-MIL-101; bdc(2-) = 1,4-benzenedicarboxylate; solv = N,N-dimethylformamide, tetrahydrofuran), the first metal-organic framework containing exclusively Ti(III) centers. Through a combination of gas adsorption, X-ray diffraction, magnetic susceptibility, and electronic and vibrational spectroscopy measurements, this high-surface-area framework is shown to contain five-coordinate Ti(III) centers upon desolvation, which irreversibly bind O2 to form titanium(IV) superoxo and peroxo species. Electronic absorption spectra suggest that the five-coordinate Ti(III) sites adopt a distorted trigonal-bipyramidal geometry that effectively shields nuclear charge and inhibits strong adsorption of nonredox-active gases

Giant coercivity and high magnetic blocking temperatures for N23- radical-bridged dilanthanide complexes upon ligand dissociation.

Increasing the operating temperatures of single-molecule magnets-molecules that can retain magnetic polarization in the absence of an applied field-has potential implications toward information storage and computing, and may also inform the development of new bulk magnets. Progress toward these goals relies upon the development of synthetic chemistry enabling enhancement of the thermal barrier to reversal of the magnetic moment, while suppressing alternative relaxation processes. Herein, we show that pairing the axial magnetic anisotropy enforced by tetramethylcyclopentadienyl (CpMe4H) capping ligands with strong magnetic exchange coupling provided by an N23- radical bridging ligand results in a series of dilanthanide complexes exhibiting exceptionally large magnetic hysteresis loops that persist to high temperatures. Significantly, reducing the coordination number of the metal centers appears to increase axial magnetic anisotropy, giving rise to larger magnetic relaxation barriers and 100-s magnetic blocking temperatures of up to 20 K, as observed for the complex [K(crypt-222)][(CpMe4H2Tb)2(μ-[Formula: see text])]

Synthesis and O₂ Reactivity of a Titanium(III) Metal–Organic Framework

Metal–organic frameworks featuring pores lined with exposed metal cations have received attention for a wide range of adsorption-related applications. While many frameworks with coordinatively unsaturated M^II centers have been reported, there are relatively few examples of porous materials with coordinatively unsaturated M^III centers. Here, we report the synthesis and characterization of Ti₃O­(OEt)­(bdc)₃(solv)₂ (Ti-MIL-101; bdc^2– = 1,4-benzenedicarboxylate; solv = <i>N</i>,<i>N</i>-dimethylformamide, tetrahydrofuran), the first metal–organic framework containing exclusively Ti^III centers. Through a combination of gas adsorption, X-ray diffraction, magnetic susceptibility, and electronic and vibrational spectroscopy measurements, this high-surface-area framework is shown to contain five-coordinate Ti^III centers upon desolvation, which irreversibly bind O₂ to form titanium­(IV) superoxo and peroxo species. Electronic absorption spectra suggest that the five-coordinate Ti^III sites adopt a distorted trigonal-bipyramidal geometry that effectively shields nuclear charge and inhibits strong adsorption of nonredox-active gases