A Molecular Boron Cluster-Based Chromophore with Dual Emission

Bromination of the luminescent borane, anti-B18H22, via electrophilic substitution using AlCl3 and Br2 yields the monosubstituted derivative 4-Br-anti-B18H21 as an air-stable crystalline solid. In contrast to the unsubstituted parent compound, 4-Br-anti-B18H21 product possesses dual emission upon excitation with UV light and exhibits fluorescence at 410 nm and phosphorescence at 503 nm, with Фtotal = 0.07 in oxygen-free cyclohexane. Increased oxygen content in cyclohexane solution quenches the phosphorescence signal. The fluorescent signal intensity remains unaffected by oxygen, suggesting that this molecule could be used as a ratiometric oxygen probe.

A Molecular Boron Cluster-Based Chromophore with Dual Emission

Bromination of the luminescent borane, anti-B18H22, via electrophilic substitution using AlCl3 and Br2 yields the monosubstituted derivative 4-Br-anti-B18H21 as an air-stable crystalline solid. In contrast to the unsubstituted parent compound, 4-Br-anti-B18H21 product possesses dual emission upon excitation with UV light and exhibits fluorescence at 410 nm and phosphorescence at 503 nm, with Фtotal = 0.07 in oxygen-free cyclohexane. Increased oxygen content in cyclohexane solution quenches the phosphorescence signal. The fluorescent signal intensity remains unaffected by oxygen, suggesting that this molecule could be used as a ratiometric oxygen probe.

A molecular boron cluster-based chromophore with dual emission

Bromination of the luminescent borane, anti-B18H22, via electrophilic substitution using AlCl3 and Br2, yields the monosubstituted derivative 4-Br-anti-B18H21 as an air-stable crystalline solid.

Development of a method for preparing octreotide derivative for diagnosis of neuroendocrine tumors

Currently the development of technologies for labeling somatostatin with technetium-99m for diagnosing radionuclide neuroendocrine tumors is under way. Somatostatin analogues are binded with technetium99m only by the preliminary addition of a chelating agent. Therefore, it is important to develop a method for preparation of an octreotide derivative by modifying octreotide with precursors: ligands with high chelating ability for its tight binding with technetium-99m. ω-Bis(pyridin-2-ylmethyl)amino)aliphatic acids can be used successfully as such precursors.The purpose of the study was to develop a method for obtaining a new octreotide derivative for diagnosing neuroendocrine tumors.Materials and methods. The somatostatin octreotide analogue was used as the object of the study; succinimid-1-yl 6-(bis(pyridin-2-ylmethyl)amino)hexanoate was used as a chelating agent. Methods of high performance liquid chromatography and mass spectrometry were used to separate and analyze the synthesized compounds.Results. A method to produce an original octreotide derivative using a succinimid-1-yl 6-(bis(pyridin2-ylmethyl)amino)hexanoate as a chelating agent was proposed. The conditions of analytical and semipreparative HPLC for the analysis and purification of the active octreotide derivative (a monosubstituted derivative of the amino acid residue of D-phenylalanine) were suggested.Conclusion. The synthesized derivative of octreotide has a chelating center for strong binding to technetium-99m in its structure, which can be useful for diagnosing neuroendocrine tumors.

Strukturen sterisch überfüllter Moleküle, 39 [1,2]

1,4-Bis(trimethylsiloxy)benzene has been crystallized both by vacuum sublimation and from «-heptane solution, which each yielded colourless plates with identical monoclinic unit cell dimensions (P2/n, Z = 4). The conformation of C[ symmetry shows the two (H3C)3SiO-substituents to be conrotationally twisted around the O-( C6H4)-O axis by dihedral angles o f ± 60°. According to the photoelectron spectroscopic ionisation pattern and its Koopmans’ assignment, IEVn = -εJAM 1, by AM 1 eigenvalues, the gas phase structure should also be of C, symmetry. The results of geometry-optimized MNDO , AM 1 or PM 3 calculations for the monosubstituted derivative H5C6-OS i(CH3)3 are compared with respect to the quality of their fit to the measured data.

Self-Association of Nicotinamide in Aqueous-Solution: N.M.R. Studies of Nicotinamide and the Mono- and Di-methyl-Substituted Amide Analogs

The concentration-dependent self-association of nicotinamide in solution has been studied by 1H and 13C n.m.r. spectroscopy, attendant relaxation time measurements, and osmometric techniques. N-Methylnicotinamide and N,N- dimethylnicotinamide were also studied to evaluate the role of the amide group in the association process. The osmometric studies indicated that the dimethyl -substituted analogue underwent little (if any) self-association, whereas nicotinamide and N- methylnicotinamide did self-associate. The concentration-dependent 1H and 13C chemical shift profiles of nicotinamide and the monosubstituted analogue indicated that the association involved the amide group and did not occur through stacking of the pyridine rings. Spin lattice relaxation (T1) studies indicated that the T1( ortho C)/T1( para C) ratio of nicotinamide decreased with increasing concentration, and that loss of a preferred axis of rotation had occurred due to formation of a large associated species. The T1 ratios of either substituted amide analogue were not concentration-dependent. The extent of self-association of the monosubstituted derivative was insufficient to affect the measured T1 ratios. These data indicate that the self-association of nicotinamide in aqueous solution occurs primarily through interamide hydrogen bonding.

Structural investigations of substituted methylenemalonaldehydes by X-ray crystallography and NMR spectroscopy

Crystal and molecular structure of three substituted methylenemalonaldehydes I-III was studied. The spatial arrangement of the monosubstituted derivative I differs significantly from that of the disubstituted methylenemalonaldehydes II and III, not only in the solid state conformation of the malonaldehyde fragment but also in the length of the ethylenic C=C double bond and in its distorsion. The structures found in crystal are compared with conformations in solutions determined by NMR spectroscopy.