Synthesis and Anion Recognition of Trinuclear Ferrocene-based Imidazole Receptors†

doi:10.7503/cjcu20140819

Abstract

Abstract:

Anions are ubiquitous in the world and play important roles in modern chemistry and life process, numerous efforts have been devoted to the design of acyclic receptors capable of selectively binding and sensing anions. Herein, several novel trinuclear ferrocene-based imidazole receptors 2a—2c were synthesized from the reactions of 1-(ferrocenylmethylene)imidazole with corresponding bromides 1a—1c. All of these receptors were characterized by ¹H NMR, ¹³C NMR, MS, IR and elemental analysis. The anion binding studies were carried out by various techniques such as electrochemistry(CV and DPV) and ¹H NMR spectroscopy. Electrochemical behavior indicated that all the receptors displayed unique electrochemical sensing property for F^- with a remarkable phenomenon: the previous peak of the free receptor gradually diminished, a new wave at more negative potential(ΔE_p>-150 mV) appeared due to the hydrogenation reaction. ¹H NMR titrations demonstrated that all the receptors could bind anions through(C—H)⁺…anion hydrogen bonds forming 1:1 stoichiometric complexes and had good fluoride binding ability in DMSO-d₆. Addition of F^-caused deprotonation effect on the receptors, indicating the receptors showed better affinity for F^-. Particularly, receptor 2b turned out to be a very good anion receptor with remarkably high preference in binding with F^-.

Key words: Ferrocenyl, Imidazole, Trinuclear, Anion recognition, Electrochemical, 1H NMR titration

CLC Number:

O626.1

TrendMD:

ZHUO Jibin, WAN Qian, YAN Xiquan, XIE Lili, YUAN Yaofeng. Synthesis and Anion Recognition of Trinuclear Ferrocene-based Imidazole Receptors^†[J]. Chem. J. Chinese Universities, 2015, 36(3): 477.

Figures/Tables 9

Scheme 1 Synthetic routes of compounds 2a—2c

Table 1 Appearance, yields, melting points, LC-MS, IR data and elemental analysis for compounds 1a—1c and 2a—2c

Compd.	Appearance	Yield^a(%)	m. p./℃	LC-MS,m/z	IR(KBr), $ν ˙$ /cm^-1	Elemental analysis(%, calcd.)
Compd.	Appearance	Yield^a(%)	m. p./℃	LC-MS,m/z	IR(KBr), $ν ˙$ /cm^-1	C	H	N
1a	White solid	22.2	101—103	445.44^b	3063, 3041, 2970, 1601, 1566, 1471, 1245, 1073, 576	32.36 (32.25)	3.48 (3.38)
1b	White solid	32.1	40—42	487.62^b	3060, 3021, 2970, 1471, 1456, 1443, 1387, 996, 582	37.02 (36.84)	4.33 (4.33)
1c	White solid	38.2	36—37	528.91^b	3063, 3041, 1601, 1588, 1497, 1471, 1377, 1274, 564	40.91 (40.71)	5.21 (5.12)
2a	Yellow solid	32.2	93—94	1294.81^c	3448, 3368, 3034,2940, 1566, 1489, 1439, 1376, 1325, 1015, 836, 497	45.29 (45.02)	4.01 (3.99)	5.72 (5.83)
2b	Yellow solid	36.4	77—78	1338.88^c	3418, 3097, 2953, 2867, 1617, 1552, 1479, 1433, 1376, 831, 491	46.27 (46.18)	4.33 (4.28)	5.80 (5.67)
2c	Yellow solid	46.2	72—73	1378.83^c	3437, 3149, 3090, 2966, 2920, 1552, 1453, 1315, 1112, 831, 493	47.49 (47.27)	4.72 (4.56)	5.69 (5.51)

Table 1 Appearance, yields, melting points, LC-MS, IR data and elemental analysis for compounds 1a—1c and 2a—2c

Compd.	Appearance	Yield^a(%)	m. p./℃	LC-MS,m/z	IR(KBr), $ν ˙$ /cm^-1	Elemental analysis(%, calcd.)
Compd.	Appearance	Yield^a(%)	m. p./℃	LC-MS,m/z	IR(KBr), $ν ˙$ /cm^-1	C	H	N
1a	White solid	22.2	101—103	445.44^b	3063, 3041, 2970, 1601, 1566, 1471, 1245, 1073, 576	32.36 (32.25)	3.48 (3.38)
1b	White solid	32.1	40—42	487.62^b	3060, 3021, 2970, 1471, 1456, 1443, 1387, 996, 582	37.02 (36.84)	4.33 (4.33)
1c	White solid	38.2	36—37	528.91^b	3063, 3041, 1601, 1588, 1497, 1471, 1377, 1274, 564	40.91 (40.71)	5.21 (5.12)
2a	Yellow solid	32.2	93—94	1294.81^c	3448, 3368, 3034,2940, 1566, 1489, 1439, 1376, 1325, 1015, 836, 497	45.29 (45.02)	4.01 (3.99)	5.72 (5.83)
2b	Yellow solid	36.4	77—78	1338.88^c	3418, 3097, 2953, 2867, 1617, 1552, 1479, 1433, 1376, 831, 491	46.27 (46.18)	4.33 (4.28)	5.80 (5.67)
2c	Yellow solid	46.2	72—73	1378.83^c	3437, 3149, 3090, 2966, 2920, 1552, 1453, 1315, 1112, 831, 493	47.49 (47.27)	4.72 (4.56)	5.69 (5.51)

Table 2 1H NMR and 13C NMR data for compounds 1a—1c and 2a—2c

Compd.	¹H NMR(400 MHz, DMSO-d₆), δ	¹³C NMR(100 MHz, DMSO-d₆), δ
1a	6.15(s, 3H, PhH), 4.28(t, J=6.2 Hz, 6H, CH₂), 3.64(t, J=6.2 Hz, 6H, CH₂)	160.04, 96.08, 68.00, 29.04
1b	6.13(s, 3H, PhH), 4.09(t, J=5.6 Hz, 6H, CH₂), 3.62(t, J=6.8 Hz, 6H, CH₂), 2.32(p, J=6.8, 5.6 Hz, 6H, CH₂)	160.59, 94.35, 65.41, 32.38, 29.97
1c	6.08(s, 3H, PhH), 3.98(t, J=5.6 Hz, 6H, CH₂), 3.50(t, J=6.8 Hz, 6H, CH₂), 2.08(p, J=7.6, 5.6 Hz, 6H, CH₂), 1.95(p, J=7.6, 6.8 Hz, 6H, CH₂)	160.59, 94.35, 65.41, 32.38, 29.97
2a	9.21(s, 3H, NCHN), 7.80(s, 3H, NCH), 7.76(s, 3H, NCH), 6.13(s, 3H, PhH), 5.19(s, 6H, CH₂), 4.59(t, 6H, J=4.8 Hz, CH₂), 4.43(t, 6H, J=4.8 Hz, CH₂), 4.25(m, 12H, PhH), 4.23(s, 15H, CpH)	159.85, 136.42, 123.30, 122.72, 95.17, 81.48, 69.36, 69.34, 69.22, 66.16, 48.88
Compd.	¹H NMR(400 MHz, DMSO-d₆), δ	¹³C NMR(100 MHz, DMSO-d₆), δ
2b	9.18(s, 3H, NCHN), 7.78(s, 6H, NCH), 6.04(s, 3H, PhH), 5.18(s, 6H, CH₂), 4.43(s, 6H, CpH), 4.31(t, J=7.0 Hz, 6H, CH₂), 4.25(d, 6H, CpH), 4.24(s, 15H, CpH), 4.96(t, J=5.6 Hz, 6H, CH₂), 2.20(dt, J=5.6, 7.0 Hz, 6H, CH₂)	160.44, 136.01, 123.03, 122.72, 94.46, 81.31, 69.37, 69.36, 69.20, 64.92, 48.85, 46.88, 29.44
2c	9.17(s, 3H, NCHN), 7.77(s, 6H, NCH), 6.06(s, 3H, PhH), 5.17(s, 6H, CH₂), 4.46(s, 6H, CpH), 4.26(s, 6H, CpH), 4.24(s, 15H, CpH), 4.23(t, J=7.6 Hz, 6H), 3.92(t, J=6.0 Hz, 6H), 1.95(dd, J=6.0, 5.6 Hz, 6H), 1.66(dd, J=6.0, 5.6 Hz, 6H)	160.77, 135.88, 122.87, 122.80, 94.35, 81.40, 69.36, 69.20, 67.24, 49.15, 48.89, 26.82, 25.87

Scheme 2 Fragmentation mechanism of receptor 3·Br

Table 3 Electrochemical data for ferrocene and 2a—2ca

Compd.	E_pa(free)	E_pc(free)	︳E_pa- E_pc︳	i_pa/ $i pc b$	E^c $1 / 2$
Ferrocene	496	429	67	1.03	458
2a	659	587	72	1.04	623
2b	653	585	68	1.03	619
2c	658	583	75	1.02	620

Table 3 Electrochemical data for ferrocene and 2a—2ca

Compd.	E_pa(free)	E_pc(free)	︳E_pa- E_pc︳	i_pa/ $i pc b$	E^c $1 / 2$
Ferrocene	496	429	67	1.03	458
2a	659	587	72	1.04	623
2b	653	585	68	1.03	619
2c	658	583	75	1.02	620

Table 4 Electrochemical data for receptors 2a—2c*

Receptor	ΔE_p/mV
Receptor	F^-	Cl^-	Br^-	I^-	AcO^-	HS $O 4 -$
2a	-152	-27	-8	-6	-34	-76
2b	-178	-16	-8	-4	-20	-98
2c	-160	-20	-18	-19	-16	-130

Table 4 Electrochemical data for receptors 2a—2c*

Receptor	ΔE_p/mV
Receptor	F^-	Cl^-	Br^-	I^-	AcO^-	HS $O 4 -$
2a	-152	-27	-8	-6	-34	-76
2b	-178	-16	-8	-4	-20	-98
2c	-160	-20	-18	-19	-16	-130

Fig.1 1H NMR titration curves of receptor 2a(A), 2b(B) and 2c(C) in DMSO-d6 by monitoring the C2 proton of imidazolium moieties ■ F-; ● Cl-; ▲ Br-; ▼ I-; ◆ AcO-; ? HSO4-.

Fig.2 Job’s plots for receptor 2b with F- in DMSO-d6

Table 5 Association constants(Ka) and binding free energies(ΔG 0—) for 1:1 complexes of receptors 2a—2c with anions in DMSO-d6 at 298 Ka

Receptor	Anion^b	$K a$ /(L·mol^-1)	-Δ $G 298 0 —$ /(kJ·mol^-1)
2a	F^-	1.12 × 10⁴	-23.1
	Cl^-	2.86 × 10³	-19.7
	Br^-	1.69 × 10³	-18.4
	I^-	8.01 × 10²	-16.6
	AcO^-	4.73 × 10³	-21.0
	HS $O 4 -$	5.52 × 10³	-21.3
2b	F^-	1.83 × 10⁴	-24.3
	Cl^-	2.55 × 10³	-19.4
	Br^-	1.71 × 10³	-18.4
	I^-	8.18 × 10²	-16.6
	AcO^-	4.80 × 10³	-21.0
	HS $O 4 -$	5.34 × 10³	-21.2
2c	F^-	1.14 × 10⁴	-23.1
	Cl^-	2.62 × 10³	-19.5
	Br^-	1.41 × 10³	-17.9
	I^-	7.47 × 10²	-16.4
	AcO^-	4.66 × 10³	-20.9
	HS $O 4 -$	5.75 × 10³	-21.4

Table 5 Association constants(Ka) and binding free energies(ΔG 0—) for 1:1 complexes of receptors 2a—2c with anions in DMSO-d6 at 298 Ka

Receptor	Anion^b	$K a$ /(L·mol^-1)	-Δ $G 298 0 —$ /(kJ·mol^-1)
2a	F^-	1.12 × 10⁴	-23.1
	Cl^-	2.86 × 10³	-19.7
	Br^-	1.69 × 10³	-18.4
	I^-	8.01 × 10²	-16.6
	AcO^-	4.73 × 10³	-21.0
	HS $O 4 -$	5.52 × 10³	-21.3
2b	F^-	1.83 × 10⁴	-24.3
	Cl^-	2.55 × 10³	-19.4
	Br^-	1.71 × 10³	-18.4
	I^-	8.18 × 10²	-16.6
	AcO^-	4.80 × 10³	-21.0
	HS $O 4 -$	5.34 × 10³	-21.2
2c	F^-	1.14 × 10⁴	-23.1
	Cl^-	2.62 × 10³	-19.5
	Br^-	1.41 × 10³	-17.9
	I^-	7.47 × 10²	-16.4
	AcO^-	4.66 × 10³	-20.9
	HS $O 4 -$	5.75 × 10³	-21.4

References 24

[1]	Wade C.R., Broomsgrove A. E., Aldridge S., Gabbai F. P.,Chem. Rev., 2010, 110(7), 3958—3985
[2]	Bai Y., Zhang B.G., Duan C. Y., Dang D. B., Meng Q. J.,New J. Chem., 2005, 29, 777—779
[3]	Dong Z.Y., Jiang X. Z., Zhang D. W., Gao G. H.,Chem. J. Chinese Universities, 2012, 33(10), 2256—2262
	(董智云, 江小枝, 张大卫, 高国华. 高等学校化学学报, 2012, 33(10), 2256—2262)
[4]	Liu W.X., Jiang Y. B.,J. Org. Chem., 2007, 73(3), 1124—1127
[5]	Nishiyabu R., Palacios M.A., Dehaen W., Anzenbacher P.,J. Am. Chem. Soc., 2006, 128(35), 11496—11504
[6]	Hossain M.A., Kang S. O., Powell D., Bowman-James K.,Inorg. Chem., 2003, 42(5), 1397—1399
[7]	Bates G.W., Gale P. A., Light M. E.,Chem. Commun., 2007, 21, 2121—2123
[8]	Kong D., Weng T., He W., Liu B., Jin S., Hao X., Liu S.,J. Organomet. Chem., 2013, 72, 19—27
[9]	Cao Q.Y., Lee M. H., Zhang J. F., Ren W. X., Kim J. S.,Tetrahedron Lett., 2011, 52, 2786—2789
[10]	Thomas J.L., Howarth J., Hanlon K., McGuirk D.,Tetrahedron Lett., 2000, 41, 413—416
[11]	Thomas J.L., Howarth J., Kennedy A.,Molecules, 2002, 7, 861—866
[12]	Bai Y., Zhang B.G., Duan C. Y., Dang D. B., Meng Q. J.,New J. Chem., 2006, 30, 266—271
[13]	Niu H.T., Yin Z., Su D., Niu D., He J., Cheng J. P.,Dalton Trans., 2008, 3694—3700
[14]	Niu H.T., Yin Z., Su D., Niu D., Ao Y., He J., Cheng J. P.,Tetrahedron, 2008, 64, 6300—6306
[15]	Liu Q.X., Yao Z. Q., Zhao X. J., Chen A. H., Yang X. Q., Liu S. W., Wang X. G.,Organometallics, 2011, 30, 3732—3739
[16]	Zhuo J. B., Zhang C. Y., Lin C. X., Bai S., Xie L. L., Yuan Y. F., J. Organomet. Chem., 2014, 34—43, 763/764
[17]	Zhuo J.B., Zhu X. X., Lin C. X., Bai S., Xie L. L., Yuan Y. F.,J. Organomet. Chem., 2014, 770, 85—93
[18]	Beer P. D., Gale P. A., Chen G. Z., Coord. Chem. Rev., 1999, 185/186, 3—36
[19]	Beer P.D., Chen Z., Ogden M. I., J. Chem. Soc.,Faraday Trans., 1995, 91, 295—302
[20]	Beer P.D., Graydon A. R., Sutton L. R.,Polyhedron, 1996, 15, 2457—2461
[21]	Boiocchi M., Del Boca L., Gómez D.E., Fabbrizzi L., Licchelli M., Monzani E.,J. Am. Chem. Soc., 2004, 126, 16507—16514
[22]	Amendola V., Boiocchi M., Fabbrizzi L., Palchetti A.,Chem. Eur. J., 2005, 11, 5648—5660
[23]	Kumar R., Guchhait T., Mani G.,Inorg. Chem., 2012, 51, 9029—9038
[24]	Thordarson P.,Chem. Soc. Rev., 2011, 40, 1305—1323