Center for Magnetic Resonance

Yu. Kondratev, A. Butlak, I. Kazakov, A. Timoshkin

“Sublimation and thermal decomposition of ammonia borane: Competitive processes controlled by pressure”

Thermochim. Acta, 2015, in press
DOI:10.1016/j.tca.2015.08.021

Thermal behavior of ammonia borane BH3NH3 (AB) has been studied by calorimetry, tensimetry and mass spectrometry methods. It is shown, that depending on vapor pressure in the system two competitive processes are taking place at 357 K. At atmospheric pressure thermal decomposition with hydrogen evolution is the dominant process: BH₃NH_3(s) = 1/n (BH₂NH₂)_n(s) + H_2(g) (1). At low pressures (circa 4 mTorr) the major process is endothermic sublimation of AB: BH₃NH_3(s) = BH₃NH_3(g) (2). At intermediate pressures both processes occur simultaneously. Enthalpies for the processes (1) and (2) have been determined by drop-calorimetry method: Δ₍₁₎H_357° = −24.8 ± 2.3 kJ mol⁻¹ and Δ_subH_357°(BH₃NH₃) = 76.3 ± 3.0 kJ mol⁻¹. Solid products after sublimation and decomposition have been characterized by IR and NMR spectroscopy; gaseous forms were studied by mass spectrometry. Activation energy of 94 ± 11 kJ mol⁻¹ for the process (1) in range 327–351 K was determined by static tensimetry method. Based on the analysis of available thermodynamic characteristics, new values for the standard formation enthalpy of solid AB −133.4 ± 5.2 kJ mol⁻¹ and polyamidoborane −156.7 ± 5.8 kJ mol⁻¹ are recommended.

A.A. Beljaev, D.V. Krupenya, E.V. Grachova, V.V. Gurzhiy, A.S. Melnikov, P.Yu. Serdobintsev, E.S. Sinitsyna, E.G. Vlakh, T.B. Tennikova, S.P. Tunik

“Supramolecular AuI-CuI complexes as new luminescent labels for covalent bioconjugation”

Bioconjugate Chem., 2015
DOI:10.1021/acs.bioconjchem.5b00563

Two new supramolecular organometallic complexes, namely, [Au₆Cu₂(C₂C₆H₄CHO)₆(PPh₂C₆H₄PPh₂)₃](PF₆)₂ and [Au₆Cu₂(C₂C₆H₄NCS)₆(PPh₂C₆H₄PPh₂)₃](PF₆)₂, with highly reactive aldehyde and isothiocyanate groups have been synthesized and characterized using X-ray crystallography, ESI mass spectrometry, and NMR spectroscopy. The compounds obtained demonstrated bright emission in solution with the excited-state lifetime in microsecond domain both under single- and two-photon excitation. The luminescent complexes were found to be suitable for bioconjugation in aqueous media. In particular, they are able to form the covalent conjugates with proteins of different molecular size (soybean trypsin inhibitor, human serum albumin, rabbit anti-HSA antibodies). The conjugates demonstrated a high level of the phosphorescent emission from the covalently bound label, excellent solubility, and high stability in physiological media. The highest quantum yield, storage stability, and luminance were detected for bioconjugates formed by covalent attachment of the aldehyde-bearing supramolecular AuI–CuI complex. The measured biological activity of one of the labeled model proteins clearly showed that introduced label did not prevent the biorecognition and specific protein–protein complex formation that was extremely important for the application of the conjugates in biomolecular detection and imaging.