Anion transport and binding properties of N N′-(phenylmethylene)dibenzamide based receptors

Figures & data

Figure 1 Bisamide based receptors 1–7.

Table 1 Apparent stability constants (M^− 1) in A) DMSO-d₆/0.5 % water and B) 59.75 % acetonitrile-d₃/39.75 % DMSO-d₆/ 0.5 % water.

	1		2		3		4		5		6		7
Anion	A	B	A	B	A	B	A	B	A	B	A	B	A	B
Cl^−	19	46	19	47	17	67	18	54	11	27	10	49	< 10	< 10
^a,b	275	550	771	1680	745	^c	796	^c	266	314	307	^c	^c	^c
	370	296	2270	1630	8290	3410	1350	4030	673	530	1320	4370	^c	^c

Notes: Guests were added as tetrabutylammonium salts, unless stated otherwise. All data was fitted to a 1:1 receptor:anion isotherm with WinEQNMR2.

a Peak broadening upon addition of the anionic guest.

b Guest was added as a tetraethylammium salt.

c No association constant could be calculated due disappearance of the NH signal upon addition of the anionic guest, most probably due to deprotonation of the receptor.

Figure 2 (Colour online) Chloride efflux facilitated by 1–7 at 2 mol% loading (with respect to lipid) from POPC vesicles containing 489 mM NaCl buffered to pH 7.2 with 5 mM sodium phosphate salts suspended in 489 mM NaNO₃ buffered to pH 7.2 with sodium phosphate salts. To end the experiment detergent was added to lyse the vesicles and this final chloride efflux was used as 100 % to calibrate the ion selective electrode. Each point is an average of three runs.

Figure 3 (Colour online) Chloride efflux facilitated by 1–7 at 2 mol% loading (with respect to lipid) from POPC vesicles containing 450 mM NaCl buffered to pH 7.2 with 20 mM sodium phosphate salts suspended in 162 mM Na₂SO₄ buffered to pH 7.2 with sodium phosphate salts. At 120 s a NaHCO₃ solution was added to give a 40-mM external concentration. To end the experiment detergent was added to lyse the vesicles and this final chloride efflux was used as 100% to calibrate the ion selective electrode. Each point is an average of three runs.

Table 2 EC₅₀ and Hill coefficient (n) values for receptors 2–6.

Receptor	EC50	n
2	^a	^a
3	5.4	0.78
4	0.37	1.07
5	^b	^b
6	3.8^c	2.5^c

Notes: To an extent all receptors tested displayed signs of self aggregation at higher concentrations, consistency of runs was hard to achieve and therefore reported Hill analysis may be unreliable.

a Hill analysis not reliable due to low transport activity.

b Possible self aggregation of the receptor did not allow for consistent results for Hill analysis.

c Hill analysis should be treated with caution due to poor fit and unusual behaviour in testing.

Figure 4 (Colour online) Chloride efflux facilitated by 2–6 at 2 mol% loading (with respect to lipid) from POPC: Cholesterol (7:3) vesicles containing 489 mM NaCl buffered to pH 7.2 with 5 mM sodium phosphate salts suspended in 489 mM NaNO₃ buffered to pH 7.2 with sodium phosphate salts. To end the experiment detergent was added to lyse the vesicles and this final chloride efflux was used as 100% to calibrate the ion selective electrode. Each point is an average of three runs. DMSO was used for the blank run.

Figure 5 (Colour online) NMR dilution studies: stack plots of spectra differing in concentration (1–100 mM) samples in DMSO- d₆. (a) Small upfield shift of proton H_a. (b) Small downfield shift of proton H_b.

Figure 6 (Colour online) (a) Uncomplexed receptors 2 and 6. (b) Self aggregation through hydrogen bonding to adjacent receptor molecules (distances in Å).