Pressure enhancement of charge-transfer complexing of 1-methyl-3-(carbomethoxy)pyridinium cation and 8-chlorotheophyllinate anion in aqueous solution

Abstract

Values have been obtained for the association constant of the acceptor l-methyl-3-(carbomethoxy)pyridinium cation with the donor 8-chlorotheophyllinate anion in aqueous solution at pH 7.0, I = 0.5, T = 25 OC, at pressures from 0.1 to 209.5 MPa. From these data the apparent volume change on association is estimated to be A V = -4.0 f 0.5 cm3 mol-', and the increment in compressibility is AK = 0.0 Pa-'. No significant change in the increment in the extinction coefficient, A€, was observed. The results are interpreted in terms of the volume changes to be expected on association due to ion pairing, charge transfer, and the approach of aromatic rings in water. IntroductionStudies on the effect of pressure on the activity of enzymes' and of the denaturation of proteins2 depend for their interpretation on a knowledge of the volume changes

Ground- and excited-state dynamic control of an anion receptor by hydrostatic pressure

“…[4][5][6] Even apart from such articial molecular machines, the creation of stimulus-responsive supramolecular architectures is a recent great trend for some applications in chemical and apoptosis sensing, [7][8][9][10][11][12] drugdelivery [13][14][15] and switchable memory systems. [16][17][18][19] Hydrostatic pressure, one of the mechanical stimuli, has attracted attention for a long time since the early 1960s, [20][21][22][23][24][25][26][27] since hydrostatic pressurization of object solutions can control not only ground-state thermodynamic equilibria in molecular recognition [28][29][30][31][32][33][34][35] and biomolecular events [36][37][38] but also excitedstate kinetic rates in photophysics and photochemical reactions. [39][40][41][42] Despite being quite an old topic, this area has come into the limelight again from the viewpoints of mechanochromic chemistry [43][44][45][46][47]…”

Hydrostatic‐Pressure‐Controlled Molecular Recognition: A Steroid Sensing Case Using Modified Cyclodextrin

“…The relatively large positive values can reasonably be accounted in terms for the elimination of the bulky branch from the CD cavity upon complexation of the guest molecule (‘naphthyl‐in’→‘naphthyl‐out’ with guest) and also solvent reorientation. Such positive volume changes were often observed in the supramolecular complexation systems, [23–33] particularly in the cyclodextrin cases [28] . We did not use the K values at the further pressurization range (≥40 MPa) in the ln K ‐ P plot, because the predominant formation of the ‘naphthyl‐out’ complex ( vide supra ) hampers the recognition reporting by the dansyl inclusion/exclusion upon addition of guests.…”

“…This is, of course, because such stimuli‐responsive chemosensors appear to be excellent candidates for applications in chemical and hazardous material sensing, [11,14–16] physicochemical properties' probing, [17–19] and apoptosis imaging for cancer therapies [20–22] . Of many sophisticated chemosensors reported so far, pressure effects on molecular recognition processes have also been investigated, [23–33] as well as the above‐mentioned stimuli ones.…”

Differential effect of pressure and temperature on the catalytic behaviour of wild‐type human butyrylcholinesterase and its D70G mutant

“…Formation of ion‐pairs is associated with positive volume changes of 10±10 mL·mol −1 because charge neutralization is accompanied by a release of water (Δ V w > 0) [22, 47, 48]. Little is known about the volume change accompanying π–cation interactions [49]; however, studies on model systems indicate that these interactions are associated with small negative volume changes [50]. At intermediate pressures (0.75–1 kbar), Δ V b became strongly negative (−60 to −150 mL·mol −1 between 10 and 35°C), suggesting an increase in organization of water molecules in the active site gorge ( Fig.…”