Deprotonation

About: Deprotonation is a research topic. Over the lifetime, 9718 publications have been published within this topic receiving 212469 citations. The topic is also known as: dehydronation & acid dissociation.

Acid-Base Equilibria of (2,2'-Bipyridyl-4,4'-dicarboxylic acid)ruthenium(II) Complexes and the Effect of Protonation on Charge-Transfer Sensitization of Nanocrystalline Titania.

Abstract: The ruthenium complexes [Ru(dcbpyH2)2(Cl)2] (1), [Ru(dcbpyH2)2(NCS)2] (2), (Bu4N)4[Ru(dcbpy)2(NCS)2] (3), and (Bu4N)2[Ru(dcbpyH)2(NCS)2] (4) were synthesized and characterized by cyclic voltammetry, UV−vis absorption, and emission, IR, Raman, and NMR spectroscopy. The absorption and emission maxima of these complexes red shifted with decreasing pH, and showed pH-dependent excited-state lifetimes. The ground-state pKa values were determined by spectrophotometeric methods, and the dissociation of protons was found to occur in two steps (pKa = 3 and 1.5). The Ru(II)/(III) couple in the complex (Bu4N)4[Ru(dcbpy)2(NCS)2] is shifted ca. 290 mV negatively with regard to that of the complex [Ru(dcbpyH2)2(NCS)2] due to the replacement of H+ by tetrabutylammonium cation. The negative shift for the dcbpy-based reduction potential is even larger, i.e., about 600 mV compared to that of the complex [Ru(dcbpyH2)2(NCS)2]. The effect of deprotonation on the performance of these complexes as photosensitizers for nanocrysta...

Nature of Urea−Fluoride Interaction: Incipient and Definitive Proton Transfer

Abstract: 1,3-bis(4-nitrophenyl)urea (1) interacts through hydrogen bonding with a variety of oxoanions in an MeCN solution to give bright yellow 1:1 complexes, whose stability decreases with the decreasing basicity of the anion (CH3COO- > C6H5COO- > H2PO4- > NO2- > HSO4- > NO3-). The [Bu4N][1·CH3COO] complex salt has been isolated as a crystalline solid and its molecular structure determined, showing the formation of a discrete adduct held together by two N−H···O hydrogen bonds of moderate strength. On the other hand, the F- ion first establishes a hydrogen-bonding interaction with 1 to give the most stable 1:1 complex, and then on addition of a second equivalent, induces urea deprotonation, due to the formation of HF2-. The orange-red deprotonated urea solution uptakes carbon dioxide from air to give the tetrabutylammonium salt of the hydrogencarbonate H-bond complex, [Bu4N][1·HCO3], whose crystal and molecular structures have been determined.

What anions do to N-H-containing receptors.

Abstract: Molecules containing polarized N−H fragments behave as H-bond donors toward anions and are widely used as receptors for recognition and sensing purposes in aprotic solvents (CHCl3, MeCN, and DMSO). We present examples of receptors containing pyrrole and urea subunits, and we discuss the stability of their H-bond complexes with a variety of anions. It is demonstrated that the stability of the 1:1 complexes is strictly related to the acidic tendencies of the receptor and to the basic properties of the anion. It may happen also that more basic anions induce the deprotonation of the receptor, if equipped with electron-withdrawing substituents. This is typically observed on interaction with fluoride, due to the formation of the very stable [HF2]- self-complex. For urea-based receptors armed with chromogenic substituents, the addition of a large excess of the anion (F-, OH-) may induce the consecutive deprotonation of both N−H fragments, processes signaled by the development of vivid colors.