Search results for " Spectroscopy"

NMR T1-Relaxation Measurements on Paramagnetic Organolanthanides: An Alternative Tool for Structure Determination in Solution

2005

1H NMR investigations were conducted on four paramagnetic organolanthanides, all bearing the tetraisopropylcyclopentadienyl ligand Cp4i (HC5iPr4) in order to verify whether or not interactions observed in the solid state are maintained in solution. In some cases variable-temperature experiments were necessary to enhance the resolution and determine the best conditions for the study. The 1D NMR spectrum could be interpreted in every case. Complementary 2D COSY experiments allowed the full attribution of the signals. T1 (1H) relaxation values were determined for all the paramagnetic complexes at the most suitable temperature, and compared with those of the diamagnetic KCp4i. The same tendency…

2021

A nickel complex incorporating an N2 O ligand with a rare η2 -N,N'-coordination mode was isolated and characterized by X-ray crystallography, as well as by IR and solid-state NMR spectroscopy augmented by 15 N-labeling experiments. The isoelectronic nickel CO2 complex reported for comparison features a very similar solid-state structure. Computational studies revealed that η2 -N2 O binds to nickel slightly stronger than η2 -CO2 in this case, and comparably to or slightly stronger than η2 -CO2 to transition metals in general. Comparable transition-state energies for the formation of isomeric η2 -N,N'- and η2 -N,O-complexes, and a negligible activation barrier for the decomposition of the lat…

Three‐in‐One Crystal: The Coordination Diversity of Zinc Polypyridine Complexes

2017

The synthesis, structural and photophysical properties of two novel zinc(II) complexes bearing the tridentate ddpd (N,N' dimethyl N,N' dipyridin 2 ylpyridine 2,6 diamine) ligand are presented. Structural investigations have been carried out by single crystal X-ray diffractometry, NMR spectroscopy and Density Functional Theory calculations, revealing a diverse coordination behavior depending on the counter ion. Spectroscopic (UV-VIS and emission spectroscopy) and theoretical techniques (density functional theory and time dependent DFT calculations) have been employed to explore the photophysical properties of the complexes.

Structure effects induced by high mechanical compaction of STAM-17-OEt MOF powders

2021

Financial support by PJ-RIC-FFABR_2017 and the EPSRC grant EPSRC industrial CASE award (grant EP/N50936X/1) are acknowledged. The research programme Nanoporous materials (P1-0021) financially supported by Slovenian Research Agency (ARRS) is acknowledged as well. Metal-organic frameworks (MOFs) are promising materials for many potential applications, spacing from gas storage to catalysis. However, the powder form of which they are generally made is not suitable, mainly because of the low packing density. Powder compaction is therefore necessary, but also challenging because of their typical mechanical fragility. Indeed, generally, they undergo irreversibly damages upon densification processe…

Thermo-Chromium: A Contactless Optical Molecular Thermometer.

2017

The unparalleled excited-state potential-energy landscape of the chromium(III)-based dye [1]3+ ([Cr(ddpd)2 ]3+ ; ddpd=N,N'-dimethyl-N,N'-dipyridin-2-yl-pyridin-2,6-diamine) enables a strong dual emission in the near infrared region. The temperature dependence of this dual emission allows the use of [1]3+ as an unprecedented molecular ratiometric thermometer in the 210-373 K temperature range in organic and in aqueous media. Incorporation of [1]3+ in biocompatible nanocarriers, such as 100 nm-sized polystyrene nanoparticles and solutol micelles, provides nanodimensional thermometers operating under physiological conditions.

Organotin(IV) derivatives containing heteroditopic pyridyl-quinolin-8-olate ligands: Synthesis and structures

2021

Abstract Six novel neutral organotin(IV) complexes, viz. [n-Bu2Sn(L4-PyAQ)2] 1, [Bz2Sn(L4-PyAQ)2] 2, [Ph2Sn(L4-PyAQ)2] 3, [Ph2Sn(L3-PyAQ)2] 4, [Bz3Sn(L4-PyAQ)] 5 and [Ph3Sn(L4-PyAQ)] 6 have been synthesized via reactions of 3/4-pyridyl-quinolin-8-ol pro-ligands, with appropriate diorganotin oxide and triorganotin hydroxide precursors, respectively. The compounds 1-6 were characterized in solution by means of NMR spectroscopy while the solid-state structures of 1, 6, and of the solvates 2·1.5C6H6, 3·0.25C6H6, 2·4·C6H6, and 5·0.5H2O were authenticated by single crystal X-ray diffraction analysis. In the solid-state, the tin centers in 1-2·4·C6H6 are hexacoordinated and reveal a distorted cis-…

A Strongly Luminescent Chromium(III) Complex Acid

2018

The synthesis, structure, reactivity, and photophysical properties of a novel acidic, luminescent chromium(III) complex [Cr(H2 tpda)2 ]3+ (23+ ) bearing the tridentate H2 tpda (2,6-bis(2-pyridylamino)pyridine) ligand are presented. Excitation of 23+ at 442 nm results in strong, long-lived NIR luminescence at 782 nm in water and in acetonitrile. X-ray diffraction analysis and IR spectroscopy reveal hydrogen-bonding interactions of the counter ions to the NH groups of 23+ in the solid state. Deprotonation of the NH groups of 23+ by using a non-nucleophilic Schwesinger base in CH3 CN switches off the luminescence. Re-protonation by using HClO4 restores the emission. In water, the pKa value of …

Interactions of a Diplumbyne with Dinuclear Transition Metal Carbonyls to Afford Metalloplumbylenes

2020

The metathesis reactions of the diplumbyne AriPr6PbPbAriPr6 (AriPr6 = −C6H3–2,6-(C6H2–2,4,6-iPr3)2) with the dinuclear metal carbonyls Mn2(CO)10, Fe2(CO)9, and Co2(CO)8 under mild conditions afforded the complexes Mn(CO)5(PbAriPr6) (1), Fe(CO)4(PbAriPr6)2 (2), and Co4(CO)9(PbAriPr6)2 (3), respectively. Complexes 1–3 were structurally characterized by single-crystal X-ray diffraction and spectroscopically characterized by 1H, 13C{1H}, 59Co{1H}, and 207Pb{1H} NMR; UV–vis; and IR methods. They are rare examples of species formed by the direct reaction of a group 14 dimetallyne with transition metal carbonyls. Complexes 1 and 2 feature Mn–Pb or Fe–Pb single bonds, whereas in 3 a Co–Pb cluster i…

Radical cation and dication of a 4H-dithieno[2,3-b:3′,2′-e][1,4]-thiazine

2017

A p-tert-butylphenyl substituted 4H-dithieno[2,3-b:3′,2′-e][1,4]thiazine was synthesized by twofold Buchwald–Hartwig coupling. The electronic properties (UV/Vis, cyclic voltammetry and spectroelectrochemistry) and the DFT- and TD DFT-calculated electronic structure reveal that the parent system and the radical cation and dication oxidation products are highly polarizable π-systems with strong charge transfer contributions. The radical cation and the dication were prepared by oxidation with antimony(V) pentachloride, giving stable deeply colored salts. EPR spectroscopy of the radical cation furnishes hyperfine coupling constants with the nitrogen nucleus and the α-thienyl protons. The dicati…

Formation of dibutyl carbonate and butylcarbamate via CO2 insertion in titanium(IV) butoxide and reaction with n-butylamine

2016

Abstract The species resulting from insertion of 12CO2 and 13CO2 into titanium(IV) butoxide is for the first time fully characterized by means of infrared and nuclear magnetic resonance spectroscopy. Results show formation of Ti-monobutylcarbonate, that easily undergoes nucleophilic attack by an aliphatic amine. The hydrolysis of the resulting species produces butylcarbamate and dibutylcarbonate as the only main products. Characterization results of the carbonate-like adduct, along with its reactivity with amine molecules open the route to new ways of CO2 utilization as building block for valuable organic compounds.