Simple and hydrolytically stable proton sponge based organic cation displaying hydrogen bonding and a number of related phenomena

Synthesis and Basicity Studies of Quinolino[7,8-h]quinoline Derivatives

Quinolino[7,8-h]quinoline is a superbasic compound, with a pK_aH in acetonitrile greater than that of 1,8-bis(dimethylaminonaphthalene) (DMAN), although its synthesis and the synthesis of its derivatives can be problematic. The use of halogen derivatives 4,9-dichloroquinolino[7,8-h]quinoline (16) and 4,9-dibromoquinolino[7,8-h]quinoline (17) as precursors has granted the formation of a range of substituted quinolinoquinolines. The basicity and other properties of quinolinoquinolines can be modified by the inclusion of suitable functionalities. The experimentally obtained pK_aH values of quinolino[7,8-h]quinoline derivatives show that N⁴,N⁴,N⁹,N⁹-tetraethylquinolino[7,8-h]quinoline-4,9-diamine (26) is more superbasic than quinolino[7,8-h]quinoline. Computationally derived pK_aH values of quinolinoquinolines functionalized with dimethylamino (NMe₂), 1,1,3,3-tetramethylguanidino (N═C(NMe₂)₂) or N,N,N',N',N″,N″-hexamethylphosphorimidic triamido (N═P(NMe₂)₃) groups are significantly greater than those of quinolino[7,8-h]quinoline. Overall, electron-donating functionalities are observed to increase the basicity of the quinolinoquinoline moiety, while the substitution of electron-withdrawing groups lowers the basicity.

Theoretical study of intramolecular hydrogen bond in selected symmetric "proton sponges" on the basis of DFT and CPMD methods

"Proton sponges," derivatives of prototypic 1,8-bis(dimethylamino)naphthalene (DMAN), exhibit remarkable basicity, which made them interesting for various experimental and theoretical studies. The details of bridged proton dynamics in protonated DMAN and its derivative denoted as TMGN (1,8-bis(tetramethylguanidino)naphthalene) were investigated on the basis of density functional theory (DFT) and Car-Parrinello molecular dynamics (CPMD) methods. Special attention was paid to the effects of symmetry of the molecular skeleton and the type of substituent on the bridged proton neighborhood statistics and dynamics. The metric parameter analyses of hydrogen bridge provided us with a conclusion that proton migration events in TMGNH⁺ are less numerous than in DMANH⁺, which can be rationalized by noticing the slower dynamics of large substituents of TMGN with respect to the smaller -N(Me)₂ groups of DMAN. The atomic velocity power spectra served as computational models of the vibrational signatures associated with the presence of the intramolecular hydrogen bond. A broad feature was registered for hydrogen bonds present in both compounds. The computations were verified by experimental data available.

Maleic anhydride proton sponge as a novel MALDI matrix for the visualization of small molecules (<250 m/z) in brain tumors by routine MALDI ToF imaging mass spectrometry

A novel MALDI matrix MAPS, able to visualize deviating metabolism in glioma using a routine MALDI-ToF-MSI procedure, is presented.

The first proton sponge-based amino acids: synthesis, acid–base properties and some reactivity

The first hybrid bases constructed from 1,8-bis(dimethylamino)naphthalene and glycine or alanine residues were synthesised and structurally characterised and unusual channels of their reactivity revealed.