(–NCH2–), 126.6, 129.4, 132.6, 132.8, 163.3 (–C(O)–) and 179.2
(–C(S)–).
945, 917, 885, 848, 831, 804, 783, 755, 726, 673, 655, 532, 486,
450, 415, 381 and 302.
{cis-[Ni(I-Et-S,O)(4,40-bipyridine-N,N0)]2}n (3). 1 (0.20 g, 0.22
mmol) was reacted with bipy (0.31 g, 2.0 mmol). The formation
of a green suspension was noted after ca. 1 h. The product was
collected and stored as a green powder.
Yield: 0.215 g, 80%. Decomp. 4160 1C. Found: C, 54.76; H,
5.34; N, 13.77; S, 9.86%. IR (KBr, 1000–300 cmꢁ1): 956, 942,
915, 887, 847, 810, 781, 754, 723, 695, 674, 654, 627, 605, 570,
528, 493, 446 and 302.
cis-[Ni(I-Et-S,O)]2 (1). H2-I-Et (3.946 g, 10.00 mmol) was
dissolved in N,N-dimethylformamide (DMF), to which a solu-
tion of Ni(CH3COO)2 ꢀ 4H2O (2.489 g, 10.00 mmol) dissolved
in H2O (200 ml) and DMF (150 ml) was added dropwise while
stirring vigorously at room temperature. The mixture was
stirred for a further 3 h, followed by addition of H2O (500
ml). Upon cooling to 4 1C in a refrigerator for 24 h, the dark
solid product was collected by centrifugation and washed
several times with small portions of water. The product, 1,
was recrystallised from chloroform/acetone to give a deep
purple powder.
Yield: 3.94 g, 4.36 mmol, 87%, mp 310–313 1C. Found: C,
48.29; H, 5.47; N, 12.18; S, 13.94. C36H48N8O4S4Ni2 requires
C, 47.91; H, 5.36; N, 12.42; S, 14.21%. dH (200 MHz, CDCl3):
1.24 (24 H, m), 3.78 (16 H, m), 8.26 (6 H, m) and 8.78 (2 H, s).
dC (50 MHz, CDCl3): 12.6 (–CH3), 13.1 (–CH3), 45.3 (–NCH2–),
45.9 (–NCH2–), 126.8, 130.0, 132.5, 136.9, 170.0 (–C(S)–) and
172.3 (–C(O)–). IR (KBr, 1000–300 cmꢁ1): 943, 920, 896, 822,
779, 755, 730, 698, 679, 661, 566, 520 and 487.
{cis-[Ni(I-Et-S,O)(1,2-bis(4-pyridyl)ethane-N,N0)]2}n (4).
1
(0.20 g, 0.22 mmol) was reacted with BPE (0.37 g, 2.0 mmol).
The reaction mixture was left to stand. After ca. 1 h, a green
suspension had formed. The product was collected as a green
powder.
Yield: 0.212 g, 76%. Decomp. 4100 1C. Found: C, 56.75; H,
5.97; N, 12.84; S, 9.13%. IR (KBr, 1000–300 cmꢁ1): 951, 918,
893, 867, 845, 827, 780, 755, 723, 693, 673, 652, 529, 468, 440
and 387.
{cis-[Ni(I-Et-S,O)(1,2-di(4-pyridyl)ethylene-N,N0)]2}n (5).
1
Coordination polymers
(0.20 g, 0.22 mmol) was reacted with DPE (0.36 g, 2.0 mmol).
The reaction mixture was left to stand. After ca. 1 h, a green
suspension had formed. Following the same procedure as for 2
above, this product was separated from the mother liquor by
centrifugation and dried with gentle heat in an oven. However,
the dry flakes of solid product were found to be dull orange-
pink in colour, as opposed to the green colour of the product
when suspended in the mother liquor. The product was pul-
verised and washed with suction in a Buchner funnel using
ethanol/water. Upon exposure to fumes of CH2Cl2, the pow-
dered substance was observed to change colour to a bright
green. On removal of the source of solvent fumes, the green
powder reverted to the orange-pink colour within a few
seconds. This colour change was found to be reproducible
upon re-exposure to the fumes of CH2Cl2. This phenomenon
was replicated with the use of chloroform, although a longer
period of exposure to the fumes was required. It was observed
that this product possesses the remarkable property of vapo-
chromism, with an especially high sensitivity to chlorinated
solvents. The process is fully reversible. The product, when
dissolved in a quantity of liquid CH2Cl2 or chloroform,
initially transformed in colour to green, but then quickly
dissociated to its starting materials—indicated by the clear
purple colour of the resultant solution.
Four products were synthesised by reacting metallamacrocyclic
complex 1 with an exo-bidentate N-donor ligand. The same
general method of preparation and collection, as described for
2 below, was applied in each case. Attempts were made to
recrystallise the solid products, but these invariably met with
either insolubility or a complete dissociation of the products
into their separate original components, as evident from an
accompanying colour change back to the original purple
colour of 1. Attempts were also made to synthesise the
products more slowly by controlling the rate of mixing of the
components, in order to encourage the growth of crystals
suitable for single-crystal X-ray diffractometry. In each case,
these attempts were unsuccessful.
Note that the yields for these products have been calculated
for a coordination polymer with a MM : BL ratio of 1 : 2 and
with no guests present.
{cis-[Ni(I-Et-S,O)(pyra-N,N0)]2}n (2). Purple complex 1 (0.20
g, 0.22 mmol) was dissolved in CH2Cl2 (50 ml). The resultant
solution was filtered through a 0.45 mm nylon filter to remove
traces of solid particles. A quantity of pyra (0.16 g, 2.0 mmol)
was similarly dissolved in CH2Cl2 and subsequently filtered.
The two solutions were heated gently, mixed together in a
beaker and left to stand. After a few minutes it was noted that
the initially clear purple reaction mixture had developed a
murky quality. After further time (ca. 30 min) an orange-green
suspension was observed. Following a further 30 min, it was
found that the suspension had thickened and separated from
the mother liquor, which retained a slight tinge of purple. After
another 2 h, the mother liquor was found to be clear and
colourless, while the suspension was observed to be lime green.
The product was centrifuged, resulting in the packing of the
suspended particles into a thick disc, that, after centrifugation,
rested on the upper surface of the mother liquor. The latter was
decanted, after which the glass centrifuge tube, still containing
the lime green solid, was placed in an oven under gentle heating
to evaporate the residual solvent. The product was removed
from the oven and collected as a flaking light green layer from
the walls of the centrifuge tube. The product, 2, was pulverised
and then washed briefly with suction in a Buchner funnel using
small amounts of ethanol/water, after which it was dried and
stored as a green powder.
Yield: 0.254 g, 91%. Decomp. 4110 1C. Found: C, 56.89; H,
5.50; N, 13.29; S, 9.84%. IR (KBr, 1000–300 cmꢁ1): 966, 951,
920, 891, 849, 821, 785, 751, 724, 695, 671, 553, 487, 446 and
323. IR (KBr with DMF, 1000–300 cmꢁ1): 983, 949, 918, 889,
865, 831, 783, 752, 725, 660, 556, 446, 408, 354 and 323. The
vapochromic property of the compound was recorded by
digital photography. An experiment to determine the rate
and extent of solvent inclusion associated with the colour
change was conducted using a levitating balance.
Instrumental methods
Melting point analysis, hot stage microscopy (HSM) and
digital photography. The behaviour of the ligand H2-I-Et and
the metallamacrocycle 1 on heating were observed using a
Reichert-Jung Thermovar hot stage microscope. The proposed
coordination polymers 2–5 were heated on a Linkam THMS
600 hot stage, which was controlled by a Linkam TP92 central
processor. Digital photographs were taken through a Nikon
SMZ-10 binocular microscope using a Sony Hyper HAD
digital video camera.
Yield: 0.198 g, 84.6%. Decomp. 490 1C. Found: C, 49.10;
H, 5.28; N, 15.49; S, 11.77%. IR (KBr, 1000–300 cmꢁ1): 957,
1418
N e w J . C h e m . , 2 0 0 5 , 2 9 , 1 4 1 6 – 1 4 2 3