Selective transport of gaseous carbon monoxide through liquid membranes using an iron(II) macrocyclic complex

Abstract

Inorg. Chem. 1985, 24, 1147-1 152 1147 complex)32 lies central at AH* = 6.3 kcal mol-I and AS* = -19.6 cal K-I mol-I. Four points are included for metalloprotein-metalloprotein reactions. Sutin, from a similar inspection of a more limited set of data for cytochrome c reactions, has suggested that metalloprotein-metalloprotein reactions are associated with more positive AH* and AS* values.38 This point does not appear to be confirmed from the more extensive comparison now possible. Implications of the correlation (and the line drawn) are that AG* -12 kcal mol-', and the isokinetic temperature is 40 OC.Since the rate constant k may be regarded as composite (=I&) whether or not limiting kinetics are observed, it can be presumed that AHo and ASo are a part of the correlation in Figure 8. A graph of all known AHo and ASo values ( Figure 9) gives an impressive correlation that is according to charge and consistent with AHo and ASo making major contribution to the separation of points in Figure 8. All the protein reactants in Figure 9 are negatively charged, with complexes 3+ (upper seven points) and 3-(lower points) and the triangle indicating parameters for the association of the 5-complex with cytochrome$ We also note that AH* values for the reactions of plastocyanin, PCu', and azurin, ACu', with [Fe(CN)6]3-and the 5-complex are negative and that the AHo component is likely to be negative therefore for these reactions.27 It is of further interest that three of the points in Figure 9 are for the [Co(4,7-DPSphen),13-complex (4,7-DPSphen = 4,7-bis(phenylsulfonato)phenanthroline), which has a large size and unusual charge distribution. A correlation for AHd* and AS&*, although giving a similar trend, shows much more scatter.The correlation in Figure 9 implies a common AGO of -4.6 kcal mol-' at a temperature close to 50 OC. On a cautionary note, we should add that although no AHo and ASo parameters are at present available for 4+ and 5+ complexes, it is unlikely that these will correlate in a similar fashion. Thus, K values for 4+ and 5+ complexes31 of -20000 M-' at 25 OC are unlikely to decrease to around 1000 M-' at 50 O C to conform to the correlation. Registry No. [(CN)5FeCNCo(CN)5]5-, 53535-93-6; [Fe(CN)6]3-, 13408-62-3; [C~(dipic)~]-, 7 1605-2 1-5; [ C~(bpy)~(O~CMe),l+, 16986-92-8; [Co(phen)J3+, 16788-34-4; [Zr(C20,),le, 21392-82-5; [Mo-(CN),le, 17923-49-8; cytochrome f, 9035-46-5. Supplementary Material Available: Listings of rate constants, Tables I-IV and VI-XI (12 pages). Ordering information is given on any current masthead page. Contribution from the The equilibrium constant and rate constants for the reversible 1: 1 complexation reaction Fe1'(TIM)(C6H5CN)?+ + CO 5 Fe11(TIM)(C6H5CN)(CO)2+ + C6H5CN have been measured in benzonitrile. At 25 OC, Kq = K/[C6H5CN] = kl'/k-, = 420 M-I, k,' = 0.14 M-' s-I, and k-, = 3.3 X ~O-'S-~.In CO-saturated solutions, the Fe(I1) complex can be oxidized electrochemically by a C,E,E,C, mechanism, which allows the diffusion coefficients of the complex and CO adduct to be determined....

Dynamics of CO Binding to Lacunar Iron(II) Cyclidene Complexes

“…The concentration of the complex was usually in the range of (1−5) × 10 -5 M, and measurements were performed in acetonitrile in the presence of 1.5 M 1-methylimidazole, with the exception of the investigations directed at the influence of solvent and axial ligand. To the best of our knowledge, the solubility of carbon monoxide in acetonitrile has not been reported, and an estimated value of 6.6 mM at 25 °C and 1 atm was used in our calculations 28a…”

On the improved absorption of carbon monoxide in the ionic liquid 1-hexyl-3-methylimidazolium chlorocuprate

“…Carbon monoxide is a key raw material in the synthetic routes for a variety of major chemical products including methanol, formaldehyde, acetic acid, isocyanates, aldehydes, formic acid, pesticides, and herbicides. It has an increased importance as raw material for liquid hydrocarbon fuels in the Fischer-Tropsch process where CO molecules are coupled to C-C bond formation [1]. All sources of carbon monoxide are essentially gas mixtures, most common being the synthesis gas, coke-oven gas and blast furnace gases [2].…”

“…The key issue in developing a separation process based on reversible complexation is the ability of a carrier to bind selectively to the permeant with appropriate equilibrium and rate constants (K eq ). For a system to be efficient enough recommended values of the equilibrium parameters by Noble et al [1] are between 2 x 10 2 M -1 and 2 x 10 4 M -1 for facilitated transport of gases in liquid membranes at solubilities around 5 x 10 -3 M and partial pressures from 1.01 x 10 4 Pa to 1.01 x 10 5 Pa. Table 1 shows the values of the equilibrium constants (K eq ) reported in the literature for CO complexation with transition metals and their ions. The magnitude of K eq for copper (I) based systems is within the recommended range and therefore copper (I) can be considered as the optimum carrier in membrane facilitated transport.…”

The transfer of neutral molecules, ions and ionic species from water to benzonitrile; comparison with nitrobenzene

“…The data that we have collected on solubility or partition of non-electrolytes is in Table 2 [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. We distinguish, for the moment, data that refers to dry benzonitrile and to wet (that is water-saturated) benzonitrile, and include in Table 2 an 'indicator variable', I, for dry or wet benzonitrile.…”