Y. Garcia et al.
sive photochromic properties claimed earlier.[16] 3) As a
result, the relationship between the dihedral angle, the elec-
tron density in photosensitive moieties and the intramolecu-
lar hydrogen-bond strength was not found to be sufficient to
predict the observed chromic phenomena, as claimed earli-
er.[18] 4) In addition, we have shown in this case that the di-
hedral angle is an independent structural parameter.
5) Thanks to a novel computational approach, we demon-
strate that the optical properties of N-salicylidene deriva-
tives cannot be predicted on the basis of the crystal struc-
ture exclusively, as claimed earlier.[18] Thus crystallography
is certainly the most important tool to investigate such mol-
ecules but must be accompanied by a wide range of physical
and theoretical methods.
We have also shown that the use of a metal ion is an easy
way to control crystal packing and tune electron density (by
replacement of the metal ion or ancillary ligands). Here, the
photosensitive L3 molecule was successfully introduced into
an inorganic framework for the first time. However, the
metal ion quenches photochromism of such complexes but
not the thermochromism. This is a very promising field.[58]
The syntheses and optical studies of a new range of N-salicyl-
ideneaniline derivatives and complexes, in which this diffi-
culty could be alleviated, is in progress in our laboratory.
The role of the metal, anion and solvent will be extensively
studied on these novel systems.
n˜ =1616 (s), 1558 (s), 1477 (s), 1425 (w), 1385 (w), 1356 (s), 1275 (s),
1182 (s), 1171 (s), 1097 (w), 1018 (w), 978 (w), 922 (w), 881 (w), 862 (m),
810 (s), 783 (m), 698 (s), 650 (m), 619 (m), 565 (m), 519 (w), 455 cmꢀ1
(w); elemental analysis calcd (%) for C12H9N2OCl (Mr =232.67 gmolꢀ1):
C 61.95, H 3.90, N 12.04; found: C 61.75, H 3.85, N 11.96; X-ray powder
diffraction pattern [8]: 9.1 (s), 14.9 (w), 15.5 (w), 17.5 (w), 18.4 (s), 19.9
(m), 20.3 (w), 24.2 (w), 27.1 (w), 27.7 (s), 28.8 (w), 30.9 (w), 31.5 (w), 33.3
(m), 40.3 (w), 52.6 (w). Single crystals were obtained by recrystallisation
in methanol and slow evaporation at room temperature.
Ligand L4: 4-Aminopyridine (2.376 g, 25.54 mmol, 1 equiv) was suspend-
ed in toluene (50 mL) in a 100 mL round-bottomed flask with a Dean–
Stark setup. Salicylaldehyde (2.7 mL, 25.26 mmol, 1 equiv) was added to
the solution leading to a slight yellow colouration. A clear solution was
obtained after leaving the solution for 24 h at reflux. Then it was concen-
trated. The resulting yellow oil was cooled in a salt/ice bath and a small
amount of precipitated impurities was filtered off. The solution was col-
lected and dried under a vacuum line to afford a pure yellow precipitate
1
(3.29 g, 66%). H NMR (300 MHz, [D6]DMSO, 298 K): d=12.30 (s, 1H),
1
2
9.00 (s, 1H), 8.65 (m, 2H), 7.75 (dd, J=7.9 Hz, J=1.7 Hz, 1H), 7.49 (m,
1H), 7.37 (m, 2H), 7.03 ppm (m, 2H); elemental analysis calcd (%) for
C12H10N2O (Mr =198.22 gmolꢀ1): C 72.71, H 5.08, N 14.13; found: C
70.92, H 5.30, N 14.03. Single crystals were obtained by sublimation
under reduced pressure (ꢁ758C, over a period of a week) on the cold
finger condenser of a sublimator apparatus.
Syntheses of complexes 1–6
(CH3OH)2(L3)
[CoACHTUNGTRENNGU 2ACHTUNGTRNE(NGUN NCS)2] (1): CoCl2·6H2O (0.091 g, 0.4 mmol, 1 equiv)
and NH4NCS (0.06 g, 0.8 mmol, 2 equiv) were each dissolved in methanol
(5 mL). The clear solution of NH4NCS was added to the red CoII solution
to give a pink solution. The resulting solution was slowly added to a
yellow solution of L3 (0.150 g, 0.8 mmol, 2 equiv, dissolved in 10 mL of
methanol) to give a clear red solution that was kept in the dark. After
seven days, red needles of X-ray diffraction quality were obtained.
[NiACTHNUGTRENNUG 2ACHTUNGTREN(NGUN NCS)2] (2): NiCl2 (0.09 g, 0.4 mmol, 1 equiv) and
(CH3OH)2(L3)
NH4NCS (0.0601 g, 0.8 mmol, 2 equiv) were each dissolved in methanol
(5 mL), mixed and added to L3 (0.1500 g, 0.8 mmol, 2 equiv) dissolved in
methanol (10 mL). Pale green needles were obtained from this green so-
lution after keeping it in darkness for seven days.
Experimental Section
Starting materials: Solvents (diethyl ether (analytical reagent), absolute
ethanol, HPLC-grade methanol from Prolabo; [D6]DMSO from Aldrich;
toluene for analysis from Fisher Chemicals) and reagents (3- and 4-ami-
nopyridine from Lancaster; l(+)-ascorbic acid, salicylaldehyde, 5-chloro-
salicylaldehyde, FeCl2·4H2O, CuCl2·2H2O, MnCl2·4H2O, KNCSe,
NH4NCS (extra pure) from Acros Organics; CoCl2·6H2O ACS reagent
from Aldrich; NiCl2 from UCB) were obtained commercially and used
as received.
[CoACHTUNGTRENNGU 2ACHTUNGTRNE(NGUN NCSe)2] (3): CoCl2·6H2O (0.090 g, 0.4 mmol, 1 equiv)
(CH3OH)2(L3)
and KNCSe (0.108 g, 0.8 mmol, 2 equiv) were each dissolved in methanol
(5 mL) and L3 (0.149 g, 0.8 mmol, 2 equiv) was dissolved in methanol
(10 mL). The clear solution of KNCSe was added to the red solution of
cobalt to give a pink solution. The resulting solution was slowly added to
the yellow solution of L3 to give a clear red solution. The solution was
placed in a controlled-atmosphere container, equilibrated with diethyl
ether vapours and covered to avoid exposure to light. After 7 d, ether dif-
fusion provided red needles.
Syntheses of L3–L5: N-Salicylidene-3-aminopyridine (L3) and N-(5-chloro-
ACHTUNGTRENNUNG
salicylidene)-3-aminopyridine (L5) were synthesised by a condensation
reaction in ethanol.[29]
[MnACHTUNGTRNENGU 2ACHTUNGTREN(NGUN NCS)2] (4): MnCl2·4H2O (0.048 g, 0.4 mmol,
(CH3OH)2(L3)
Ligand L3: 3-Aminopyridine (4.75 g, 1 equiv, 50.4 mmol) in ethanol
1 equiv) and NH4NCS (0.060 g, 0.8 mmol, 2 equiv) were each dissolved in
methanol (5 mL) and L3 (0.15 g, 0.8 mmol, 2 equiv) was dissolved in
methanol (10 mL). The solution of NH4NCS was added to the manganese
solution to give a colourless solution that was slowly added to the solu-
tion of L3 to afford a clear yellow solution. This solution containing the
target compound in methanol was placed in the dark. Slow solvent evap-
oration over six months provided a few black single crystals.
(75 mL) was reacted with salicylaldehyde (5.3 mL, 1 equiv, 50.3 mmol) to
give L3 as
a
yellow powder (8.91 g, 89%). 1H NMR (300 MHz,
[D6]DMSO, 298 K): d=12.65 (s, 1H), 9.03 (s, 1H), 8.66 (d, J=2.5 Hz,
1H), 8.54 (dd, 1J=4.7 Hz, 2J=1.3 Hz, 1H), 7.88 (m, 1H), 7.71 (dd, 1J=
2
7.9 Hz, J=1.6 Hz, 1H), 7.49 (m, 2H), 7.02 ppm (m, 2H); elemental anal-
ysis calcd (%) for C12H10N2O (Mr =198.22 gmolꢀ1): C 72.71, H 5.08, N
14.13; found: C 72.61, H 5.09, N 14.14; X-ray powder diffraction pattern
[8]: 8 (m), 9.2 (m), 11.9 (s), 12.6 (w), 16.0 (s), 18.0 (m), 19.6 (m), 20.6 (m),
24 (m), 31.4 (w), 32.2 (m), 33.0 (w), 34.1 (w), 42.2 (w), 45.9 (w). Single
crystals were obtained by sublimation under reduced pressure (ꢁ758C,
over a period of a week) on the cold finger condenser of a sublimator ap-
paratus. An X-ray investigation revealed the same cell parameters as
those in ref. [46].
[CuACHTUNGTRENNGU 2ACHTUNGTRNE(NGUN NCS)2] (5): CuCl2·2H2O (0.064 g, 0.4 mmol, 1 equiv)
(CH3OH)2(L3)
and NH4NCS (0.06 g, 0.8 mmol, 2 equiv) were each dissolved in methanol
(5 mL) and L3 (0.150 g, 0.8 mmol, 2 equiv) was dissolved in methanol
(10 mL). The colourless solution of NH4NCS was added to the green
copper solution. The resulting solution was heated to ꢁ708C and slowly
added to the solution of L3 to give a green solution with a green precipi-
tate, which was filtered. After cooling to room temperature, small single
crystals were obtained as a result of immediate nucleation. These crystals
were allowed to grow over six months in darkness, in the mother liquor.
(CH3OH)2(L3)
[FeACHTUNGTRENNUG 2ACHTUNGTREN(NUGN NCS)2] (6): FeCl2·4H2O (0.01 g, 0.5 mmol, 1 equiv)
with a pinch of ascorbic acid (to avoid iron oxidation) was dissolved in
methanol (5 mL). NH4NCS (0.077 g, 1 mmol, 2 equiv) was also dissolved
in the same solvent (1 mL). The iron solution was added under stirring to
Ligand L5: 3-Aminopyridine (0.900 g, 1 equiv, 9.6 mmol) in ethanol
(8 mL) was reacted with 5-chlorosalicylaldehyde (1.500 g, 1 equiv,
9.6 mmol) in ethanol (7 mL) to give L5 as a yellow powder (1.83 g, 82%).
M.p. (onset temperature observed by DSC) 136(1)8C; 1H NMR
(300 MHz, [D6]DMSO, 298 K): d=12.4 (s, 1H), 8.99 (s, 1H), 8.64 (d, J=
1
2
2.5 Hz, 1H), 8.53 (dd, J=4.7 Hz, J=1.4 Hz, 1H), 7.86 (m, 1H), 7.79 (d,
J=2.7 Hz, 1H), 7.50 (m, 2H), 7.04 ppm (d, J=8.8 Hz, 1H); FTIR (KBr):
4340
ꢂ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 4327 – 4342