14066-85-4Relevant articles and documents
The effect of organic cations on the electronic, optical and luminescence properties of 1D piperidinium, pyridinium, and 3-hydroxypyridinium lead trihalides
Bahnemann, D. W.,Emeline, A. V.,Kevorkyants, R.,Rozhkova, Yu. A.,Selivanov, N. I.
, p. 4390 - 4403 (2020)
We present a structural and optoelectronic study of 1D piperidinium, pyridinium, and 3-hydroxypyridinium lead trihalides. In contrast to the piperidinium and pyridinium species whose single inorganic chains [PbX31-]n are separated by organic cations, the 3-hydroxypyridinium compound is characterized by double inorganic chains. According to DFT the valence and conduction bands of the piperidinium lead trihalides are composed of occupied p-orbitals of the halogen anions and unoccupied p-orbitals of the Pb2+ cations. In contrast, the pyridinium species feature low-lying cationic energy levels formed from the cation's π?-orbitals. Thus, electronic transitions between the cationic energy levels and valence bands require less energy than valence to conduction band transitions in the case of piperidinium lead trihalides. The presence of an OH group in the pyridinium ring leads to a bathochromic shift of the cationic energy levels resulting in a decreased energy of transitions from the cationic energy levels to the valence band. Electronic transitions predicted by DFT are observable in experimental optical absorption and luminescence spectra. This study paves the way for creation of 1D perovskite-like structures with desired optoelectronic properties.
4-Hydroxyphenacyl Ammonium Salts: A Photoremovable Protecting Group for Amines in Aqueous Solutions
Bownik, Iwona,?ebej, Peter,Literák, Jaromír,Heger, Dominik,?imek, Zdeněk,Givens, Richard S.,Klán, Petr
, p. 9713 - 9721 (2015/10/12)
Irradiation of N-protected p-hydroxyphenacyl (pHP) ammonium caged derivatives at 313 nm releases primary and secondary amines or ammonia in nearly quantitative yields via the photo-Favorskii reaction when conducted in acidic or neutral aqueous buffered media. The reaction efficiencies are strongly dependent on the pH with the most efficient and highest yields obtained when the pH of the media maintains the ammonium and p-hydroxyl groups as their conjugate acids. For example, the overall quantum yields of simple secondary amines release are 0.5 at acidic pH from 3.9 to 6.6 dropping to 0.1 at neutral pH 7.0 and 0.01 at pH 8.4. Speciation studies provide an acid-base profile that helps define the scope and limitations of the reaction. When the pKa of the ammonium group is lower than that of the phenolic hydroxyl group, as is the case for the α-amino-protected amino acids, the more acidic ammonium ion deprotonates as the media pH is changed from acidic toward neutral or basic, thus diminishing the leaving group ability of the amino group. This, in turn, lowers the propensity for the photo-Favorskii rearrangement reaction to occur and opens the reaction pathway to alternative competing photoreduction process.
CATALYSIS IN THE FORMATION OF α-AMINO KETONES
Popov, A. F.,Anikeev, A. V.
, p. 939 - 944 (2007/10/02)
The kinetics of the reaction of α-halogenoacetophenones with piperidine and N-methylpiperidine in cyclohexane at 30 deg C were investigated.The autocatalytic nature of these reactions is due to the formation of catalitically active acidic products from degradation of the α-aminoacetophenone in the reaction system.The catalytic effect of additions of acetic acid and phenol on the rate of the reactions of α-halogenoacetophenone with piperidine and N-methylpiperidine is described quantitatively.Catalysis by acetic acid in the reactions of α-halogenoacetophenones with piperidine has a bifunctional mechanism.
