JOURNAL OF CHEMICAL RESEARCH 2009 127
H, 9.80; N, 9.76%. 1H NMR (CDCl3) 1.30 (18H, s), 1.44 (18H, s), 2.61
(12H, m), 3.74 (4H, t), 7.06 (2H, s), 7.38 (2H, s), 8.36 (2H, s), 13.72(2H,
s); 13C NMR (CDCl3) 29.54, 31.59, 34.19, 35.09, 53.50, 57.12, 58.98,
118.04, 125.88, 126.94, 136.82, 140.08, 158.23, 166.78.
Found: C, 74.55; H, 7.60; N, 10.53%. 1H NMR (CDCl3) 1.81 (2H, m),
2.41 (12H, m), 3.58 (2H, t), 6.80–7.80 (12H, m), 8.64 (2H, s), 14.23
(2H, b); 13C NMR (CDCl3) 27.44, 50.69, 53.03, 106.49, 117.73, 122.63,
125.22, 126.21, 127.94,129.27, 131.75, 133.99, 137.26, 158.22.
N, N'-Bis[(pyridin-2-ylmethylene)propyl]piperazine (L10): Calcd
for C22H32N6: C, 69.44; H, 8.48; N, 22.09. Found: C, 70.25; H, 8.02;
N, 22.09%. 1H NMR (CDCl3) 1.75 (4H, m), 2.33 (12H, m), 3.53 (4H,
t), 7.13 (2H, t), 7.56 (2H, t), 7.78 (2H, d), 8.22 (2H, s), 8.47 (2H,
d); 13C NMR (CDCl3) 26.98, 52.26, 55.21, 58.38, 120.20, 123.71,
135.53, 148.38, 153.70, 161.10.
N, N'-Bis[(pyridin-2-ylmethylene)ethyl)]piperazine (L4): Calcd
for C20H26N6.0.5H2O: C, 66.82; H, 7.57; N, 23.38. Found: C, 67.23;
1
H, 7.46; N, 23.50%. H NMR (CDCl3) 2.56 (8H, br), 2.68 (4H, t),
3.78 (4H, t), 7.27 (2H, t), 7.67 (2H, t), 7.90, (2H, d), 8.34 (2H, s),
8.58 (2H, d); 13C NMR (CDCl3) 52.80, 57.67, 57.99, 120.70, 125.09,
136.95, 149.34, 153.91, 162.39.
N, N'-Bis[2-(thiophen-2-ylmethyleneamino)ethyl]piperazine (L5):
Calcd for C18H24N4S2: C, 59.96; H, 6.71; N, 15.54. Found: C, 61.30;
H, 6.58; N, 15.80%.1H NMR (CDCl3) 2.53 (8H, br), 2.63 (4H, t), 3.66
(4H, t), 6.86 (2H, d), 7.38 (4H, m), 8.28 (2H, s); 13C NMR (CDCl3)
53.68, 58.77, 58.85, 127.77, 128.77, 130.57, 142.39, 155.19.
N, N'-Bis{2-[(3-propylimino)methy)]phenol}piperazine (L6): Calcd
for C24H32N4O2: C, 70.56; H, 7.90; N, 13.71. Found: C, 71.48; H, 8.02;
N, 13.89%. 1H NMR (CDCl3) 1.87 (4H, m), 2.37 (12H, m), 3.58 (4H, t),
6.79–7.31 (8H, m), 8.20 (2H, s), 13.51 (2H, br); 13C NMR (CDCl3) 27.81,
53.08, 55.69, 57.27, 116.89, 118.29, 131.01, 131.96, 161.25, 164.88.
N, N'-Bis{2-[(3-propylimino)methyl]-5-bromophenol}piperazine (L7):
Calcd for C24H30Br2N4O2: C, 50.90; H, 5.34; N, 9.89. Found: C,
51.40; H, 5.02; N, 10.24%. 1H NMR (CDCl3) 1.81 (4H, m), 2.35
(4H, t), 2.40 (8H, br), 3.58 (4H, t), 6.79 (2H, d), 7.28 (2H, s),7.31
(2H, d) 8.20 (2H, s), 13.49 (2H, br); 13C NMR (CDCl3) 27.79, 53.20,
55.76, 57.40, 109.83, 119.11, 120.09, 160.48, 163.77.
Preparation of complex
Co(ClO4)2.6H2O(0.184g,0.5mmol)wasdissolvedinmethanol(20mL)
and added to a solution of L4 (0.18 g, 0.50 mmol) in methanol
(30 mL). The mixture was heated to reflux during 6 h and then it was
cooled. As a precipitate did not develop immediately the solution was
partially concentrated to give a solid. The product was filtered off and
dried in a vacuum. (Scheme 2).
[CoL4](ClO4)2.0.5H2O (62%). (Calcd for C20H26Cl2CoN6O6.0.5H2O:
C, 38.91; H, 4.41; N, 13.61. Found: C, 38.60; H, 4.72; N, 13.39%).
n
max/cm-1 (KBr disc): 3418 (O–H), 1643 (C=N)imine, 1598, 1446
(C=N)py, 1088, 623 (ClO4); FAB-MS m/z (%) 508 [CoL4]+ (ClO4)
(92.8), 409 [CoL4]+ (100). LM/W-1 cm2 mol-1 (in DMF): 126.4 (2:1).
Result and discussion
Here, we report synthesis of some hexadentate Schiff-base ligands,
L1–L10, derived from the condensation of N,N-bis(3-aminopropyl)
piperazine or N,N'-bis(2-aminoethyl)piperazine and a number of
different aldehydes such as salicaldehyde derivatives, thiophene-
2-carbaldehyde, 2-hydroxy-1-napthaldehyde and pyridine-2-
carbaldehyde. Their spectral data are completely consistent with the
proposed formulations. The yields, melting points, IR and EI mass
data are given in Table 1.
N, N'-Bis{2-[(3-propylimino)methyl]-4,6-di-tert-butylphenol}piperazine
(L8): Calcd for C40H64N4O2.0.35H2O: C, 75.15; H, 10.20; N, 8.76. Found:
C, 74.27; H, 11.10; N, 8.50%. 1H NMR (CDCl3) 1.33 (18H, s), 1.47 (18H,
s), 1.90 (4H, br), 2.51 (12H, br), 3.64 (4H, t), 7.10 (2H, s), 7.39 (2H, b),
8.37(2H, b), 13.89(2H, s); 13C NMR (CDCl3) 27.80, 53.20, 53.30, 55.76,
57.40, 109.83, 119.11, 120.09, 133.24, 134.80, 160.48, 163.77.
N, N'-Bis{2-[(3-propylimino)methyl]naphthalen-1-ol}piperazine (L9):
Calcd for C32H36N4O2·0.5 CH3CH2OH: C, 75.56; H, 7.13; N, 11.01.
Table 1 Synthesis of L1–L10
Structure
Ligand
L1
R
M.p/°C
150
Yield/%
80
MS m/z/% M+
IR (nC=N)
HO
380(35)
1634
HO
L2
188
85
538(50)
1634
Br
N
N
R
R
N
N
HO
L3
L4
167
102
87
80
604(30)
350(43)
1633
1647
N
S
L5
L6
L7
97
97
86
82
85
360(22)
408(65)
566(20)
1633
1634
1635
HO
HO
107
Br
N
R
R
N
N
HO
L8
125
169
84
632(35)
1631
N
OH
L9
75
81
508(20)
378(22)
1645
1650
L10
–
a
N
aThe product was an oil.
PAPER: 08/0132