A, B) Packing dia com 4B
5.3 Metal complexation of fl
L1H2, would exible dicarboxylic acid
In this subsection we have described the metal complexation behaviour of flexible dicarboxylic acid. In this context we have chosen (3-carboxymethoxy-naphthalen-2-yloxy)- acetic acid which is a flexible dicarboxylic acid and studied its metal complexation property.
The (3-carboxymethoxy-naphthalen-2-yloxy)-acetic acid(5.5), abbreviated as L1H2, has two carboxylic acid groups with flexible arms. So, it is suitable for synthesis of cyclic or open chain polymeric structures with metal ions. The two ether oxygen atoms of
provide supramolecular features like a podand. Moreover, the naphthalene ring of the ligand L1H2 might contribute to π-interactions.
Zn(OAc)2. 2H2O, CH3OH
2 Pyridine (Py)
{[Zn(L1)(Py)2(H2O)(CH3OH)].H2O}n Zn(OAc)2 2H2O
CH3OH {[Na2Zn2(L1)2 (OH)2]}n CH3OH
NaOH Na2L1
O
O OH
OH O
O 2 Zn(OAc)2.2H and DMF
N 2O, CH3OH
{[Zn(L1)(Pyz)3]. DMF}n
NH
(Pyz) 2{[Z z)4(H2O)
duct (5.1 5
N
+ Major product
n4(L1)4(Py Minor pro
8]. DMF}
0) (5.9) NaOH/Zn(OAc)2.2H2O,
NH (Pyz)
[NaZn(L1)(CH CH3OH
5.6
5.7
3COO)(Pyz)]2 (MeOH)2 5.8
Zn(OAc)2.2H2O, MeOH
[Zn(L1)(Bipy)2] 7H2O
N
( Bipy) 2
Zn(OAc)2. MeOH
N 2H2O,
N
( Phen) 2
[Zn(L1)(Phen)2] 3H2O
N L1H2(5.5)
5.11
5.12
Scheme 5.4
ydrate, (3-carboxymethoxy-naphthalen-2-yloxy)- cetic acid (L1H2) and sodium hydroxide in methanol react to form an one dimensional co- ordination polymer 5.6 having a composition {[Na2Zn2 (L1)2(OH)2]}n. The complex is unusual as it binds to sodium ions due to formation of a macrocycle like structure. Metal carboxylates having cryptand type of structure are studied in literature330. The self-assembly via metal coordination also forms macrocyclic and cage-like hosts; these exhibit potential applications in molecular encapsulation, chemosensing, catalysis and in organic synthesis9, 331-334.
The crystal structure of the complex 5.6 shows that it is a network of metallacycles formed by the ligand L1 with zinc ions. Each zinc ion in the complex 5.6 has a distorted tetrahedral coordination environment (Figure 5.13). The zinc ions are co-ordinated to four independent oxygen atoms of four carboxylate groups. The lone pairs of the oxygen on the rings project in inward direction, having resemblance to structure of crown ether. Each metallacycle holds a sodium ion through co-ordination of oxygen atoms (similar to the one generally observed in crown ethers). In complex 5.6, two carboxylates of each L1 are attached to two independent zinc ions and construct repeated units of cyclic networks. The cyclic units of the complex bind two sodium ions. The sodium ions are held by oxygen atoms with distances Na1−O1, 2.423(15)Å; Na1−O1′, 2.446(16)Å; Na1−O7, 2.372(3)Å; Na1−O5, 2.379(14); Na1−O4, 2.453(14) and Na1−O3, 2.480(15) (Table 22 in Appendix). There is also side on π-cation interaction between sodium and the C8-C9 double bond with a distance of separation 3.182Å.
All these contribute to the formation of spirane type of structure around each zinc centers.
In this study several zinc (II) complexes of L1H2 are prepared as illustrated in Scheme 5.4.
Stoichiometric amount of zinc(II) acetate dih a
Figure 5.13 Crystal packing of complex 5.6 [′= 1/2-x, 1/2-y, 1-z].
The hydrogens of hydroxide ions are involved in O7−H····O6 [dO7····O6 3.005 Å, <D−H····A 159.6º] hydrogen bonding interaction with the carboxylate oxygen. The complexes are also assembled in the lattice through weak C11−H····O6 [dC11····O6 3.331 Å, <D−H····A 166.8º]
Figure 5.25).
he hydroxyl group of the complex shows a strong IR absorption at 3550 cm-1. The icarboxylic acid L1H2 has 1H NMR signals at 7.70, 7.31, 7.24 ppm due to the three equivalent sets of aromatic protons but in the complex (5.6) the aromatic protons appear as four broad peaks at 7.74, 7.61, 7.49, 7.33 ppm.
Table 5.8: Hydrogen bond geometry(Å, °) for complex 5.6
D−H···A d(D−H) d(H···A) d(D···A) <D−H···A interaction. The hydrogen bond parameters are given in Table 5.8. The distance between two zinc atoms in the polymeric structure is 9.021 Å. The solid state FT-IR spectra of the complex 5.6, shows a strong absorption at 1643 cm-1 due to C=O stretching frequency. A medium absorption at 2902 cm-1 due to the presence of –CH2− group and two strong absorption bands at 1259 cm-1 and 1054 cm-1 for C−O stretching of ether groups are observed (
T d
O(7)−H(7O)····O(6) [1-x, y, 1/2-z] 0.82 2.22 3.005(3) 159.6 C(11)−H(11)····O(6) [1-x, -y, 1-z] 0.93 2.42 3.331(2) 166.8
This happens due to asymmetry imposed on the naphthalene ring through the complexation of the ligand. The -CH2- protons of the ligand (5.5) appear as sharp singlet at 4.80 ppm, shifts to 4.65 ppm as broad singlet in the complex 5.6. The -OH signal of the complex appears
singlet at mol-1 in
imethylsulfoxide, which suggests it to be ionic.
roup is hydrogen-bonded (intra-molecular) to the ydrogen atom of the coordinated methanol molecule by O8−H····O2 [dO8····O2 2.699 Å,
<D−H····A 170.4º] in intramolecular
h onding with the coordinated lecule through O 5 [ 7 Å,
< on.
as 7.95 ppm. The complex has a molar conductance value 94.86 S cm-1
d
A similar reaction of zinc(II) acetate dihydrate with L1H2 and subsequent treatment with pyridine in methanol (Scheme 5.4) results in polymeric complexes having composition {[Zn(L1)(Pyridine)2(H2O)(CH3OH)].H2O}n (5.7). The crystal structure of the polymer 5.7 is shown in Figure 5.14. In the complex 5.7, each zinc(II) ion has a distorted octahedral geometry, where two pyridine molecules are in cis orientation to each other. The two monodentate carboxylate groups are trans to each other in the complex. The rest of the co- ordination sites are occupied by solvent molecules namely water and methanol. One encapsulated water molecule is also present in the lattice and forms hydrogen bond with polymeric chains. One carboxylate g
h
interaction and another carboxylate is involved
ydrogen-b water mo 7−H····O dO7····O5 2.63
D−H····A 155.8º] interacti
Figure 5.14 Formation of layered structures through hydrogen bonding with interstitial water molecules in the complex 5.7 [′= 1+x, 1/2-y, 1/2+z]
In the crystal lattice, the polymeric chains are held together via inter-molecular hydrogen bonding through water molecules and form a layered structure. The water molecules between the layers are inter-molecularly hydrogen-bonded with oxygen atom of carboxylates via O9−H····O2 [dO9····O2 2.835 Å, <D−H····A 177.2º] and O9−H····O5 [dO9····O5 2.725 Å, <D−H····A
Table 5.9: Hydrogen bond geometry(Å, °) for complex 5.7
D−H···A d(D−H) d(H···A) d(D···A) <D−H···A 151.8º] interactions.
O(7)−H(7A)····O(9) [x,-1+y,-1+z] 0.80(4) 1.87(4) 2.672(4) 178.5(6) O(7)−H(7B)····O(5) [ 1+x,1/2-y,1/2+z] 0.95(8) 1.74(8) 2.637(6) 155.8(5) O(8)−H(8O)····O(2) 0.68(5) 2.02(5) 2.699(5) 170.4(4) O(9)−H(9A)····O(2) [1-x, 1-y, 1-z] 1.00(9) 1.83(9) 2.835(6) 177.2(8) O(9)−H(9B)····O(5) [1-x,1/2+y,1/2-z] 0.94(6) 1.86(7) 2.725(6) 151.8(5) C(2)−H(2A)····O(2) [ 1-x,-y,-z] 0.97 2.57 3.506(5) 162.8 C(22)−H(22)····O(8) [x,1/2-y,-1/2+z] 0.93 2.54 3.355(7) 147.2
Bes nnected by weak C22−H····O8 [dC2 ·O8
H····A 162.8º] interactions.
1595 cm-1 due to C=O stretching equency and it also shows weak absorptions at 2927 and 2922 cm-1 due to the presence of – CH2− group (Figure 5.26). Thermogravimetric analysis of the complex 5.7 shows the loss of
ides this, the polymeric chains are also interco 2···
3.355 Å, <D−H····A 147.2º] and C2−H····O2 [dC2····O2 3.506 Å, <D−
The hydrogen bond parameters are included in Table 5.9. The solid state FT-IR spectra of the complex 5.7 shows strong absorptions at 1606 and
fr
have a distorted square pyramidal geometry.
two water and a coordinated methanol molecules in the temperature range 40-100°C which corresponds to 14.27% of the total weight. The calculated weight loss is 12.02%. In the temperature range 210-290°C the complex loses the remaining two coordinated pyridine molecules with a weight loss of 38.06% (calculated weight loss is 40.00%).
The reaction of zinc(II) acetate with L1Na2 in the presence of pyrazole lead to the formation of a dinuclear zinc(II) complex, {[NaZn(L1)(CH3COO)(Pyz)]2.2MeOH} (5.8) (where pyz is pyrazole). The zinc atoms in the complex
A B
number six with Na−O bond distances Na1−O1, 2.391(19)Å, Na1−O3, 2.557(19)Å; Na1−O4, 2.519(19)Å; Na1−O5, 2.420(2)Å; Na1−O5′, 2.431(2)Å and Na1−O9, 2.313(3)Å (Table 24 in Appendix). The complex has a highly symmetric structure, with a center of inversion located at the central point of the rectangle formed by the Na2O2 units. The complex 5.8 self-assembles through intra and intermolecular N2−H····O2 [dN2····O2 2.946 Å, <D−H····A 138.4º] and N2−H····O2′
[dN2····O2′ 3.052 Å, <D−H····A 134.7º] interactions respectively (Figure 5.15B). The hydrogen atoms of naphthalene ring are involved in weak C7−H····O8 [dC7····O8 3.597 Å, <D−H····A 161.4º] and C11−H····O7 [dC11····O7 3.519 Å, <D−H····A 154.9º] interactions with the acetate Figure 5.15 A) Crystal structure of complex 5.8 [′= -x, 1-y, 2-z] and B) one dimensional molecular assembly of complex 5.8
Each zinc(II) ion is coordinated through one pyrazole molecule, two carboxylates from two independent ligands as well as a chelating acetate ligand (Figure 5.15A). The dicarboxylate ligand L1 acts as bridging ligand and results in formation of a structure having resemblance to macrocycle, which anchored the sodium ions. Besides this, one molecule of methanol is coordinated to sodium. The sodium ions have coordination
oxygens. The hydrogen bond parameters are given in Table 5.10. Besides that the sodium ions are involved in cation-π interaction with C6 and C7 atoms of the naphthalene ring with a separation of 3.957 Å. The C=O stretching frequency of the complex appears at 1620 cm-1 and strong C−O stretching frequencies are observed at 1256 cm-1 and 1061 cm-1 in the FT-IR spectra.
Table 5.10: Hydrogen bond geometry(Å, °) for complex 5.8
D−H···A d(D−H) d(H···A) d(D···A) <D−H···A N(2)−H(2N)····O(2) [Intra] 0.86(5) 2.25(5) 2.946(3) 138.4(4) N(2)−H(2N)····O(2′) [-x, -y, 1-z] 0.86(5) 2.38(5) 3.052(3) 134.7(4)
C(7)−H(7)····O(8) 0.93 2.70 3.597 161.4
C(11)−H(11)····O(7) 0.93 2.65 3.519 154.9
C(13)−H(13B)····O(7) 0.97 2.62 3.486 147.9
When we carried out the reaction of L1H2 with zinc(II) acetate dihydrate and pyrazole in the absences of sodium hydroxide in a mixed solvent of methanol and dimethylformamide (DMF) it results in the formation of an one dimensional co-ordination polymer {[Zn(L1)(Pyz)3].DMF}n (5.9) as the major product. In this reaction a cyclic tetranuclear zinc complex [Zn4(L1)4(Pyz)4(H2O)8].DMF (5.10) is also formed (Scheme 5.4).
Fig. 5.16 The crystal structure of complex 5.9 showing the hydrogen bonding interactions [′=
1+x, 1/2-y, 1/2+z]
The complex 5.9 has a zig-zag chain like structure (Figure 5.16). The zinc ions are in trigonal bipyramidal geometry formed by three coordinating pyrazoles and two monodentate carboxylates. Three nitrogen atoms form the triangular plane of the trigonal bipyramidal geometry. The bond angles <N1−Zn1−N5 and <N3−Zn1−N5 are 128.2(11)º and 124.8(11)º respectively whereas the angle <N1−Zn1−N3 is 106.7(12)º. The bond distances around the zinc centers are Zn1−N1, 2.057(3)Å; Zn1−N3, 2.023(3)Å; Zn1−N5, 2.035(3)Å; Zn1−O1, 2.196(2)Å and Zn1−O6, 2.072(2)Å (Table 25 in Appendix). The N−H hydrogen of pyrazole
Å, D−H····A 170.2º] interactions (Table 5.11).Dimethylformamide (DMF) molecules are held in the lattice through intermolecular C13−H····O7 [dC13····O7 3.380 Å, <D−H····A 170.8º]
hydrogen bonding interactions with the –CH2− groups of dicarboxylic acid. The polymeric chains are self-assembled via intermolecular C2−H····O5 [dC2····O5 3.407 Å, <D−H····A 157.5º]
and C11−H····O2 [dC11····O2 3.205 Å, <D−H····A 153.0º] hydrogen bonding interactions.
Table 5.11: Hydrogen bond geometry(Å, °) for complex 5.9
D−H···A d(D−H) d(H···A) d(D···A) <D−H···A
molecules form intramolecular hydrogen bond with the oxygen atom of carboxylic acids through N6−H····O2 [dN6····O2 2.713 Å, <D−H····A 173.9º] and N2−H····O3 [dN2····O3 3.330
<
N(2)−H(2N)····O(3) 0.86 2.48 3.330(4) 170.2
N(4)−H(4N) 6(3)
N(6)−H(6N)····O(2) 0.82(5) 1.90(5) 2.713(4) 173.9(5)
····O(5) [1+x, 1/2-y, 1/2+z] 0.95(5) 1.78(5) 2.724(4) 167.
C(2)−H(2A)····O(5) [1+x, y, z] 0.97 2.49 3.407(5) 157.5 C(11)−H(11)····O(2) [-1+x, y, z] 0.93 2.35 3.205(5) 153.0
C(13)−H(13A)····O(7) 0.97 2.42 3.380(6) 170.8
The complex in the solid state has C=O stretching of DMF at 1652 cm-1, whereas a strong absorption at 1600 cm-1 for C=O stretching of carboxylate is also observed. The thermogravimetric analysis of the complex 5.9 shows the loss of three pyrazole molecules at the temperature range 170-270ºC which corresponds to 42.17% of the total weight. The calculated weight loss is 44.89%.
The minor product in the above reaction is the tetranuclear zinc complex 5.10. It may considered to be a co-crystal of two tetra-nuclear cyclic zinc complexes; one of them has a
MF within the cyclic part and other does not (Figure 5.17). The structure also contains a
water molecule, esidual electron
d ld not be assigned. Neverthe tu ati en scribe
t he unit of th ms ctahedral
g ato ve tr -bipyramidal geometry. Zinc atoms
aving octahedral geometry are co-ordinated to three water molecules, one pyrazole and two D
hydrogen atom of which could not be located and some r
ensity cou less struc ral inform on is good ough to de he symmetry non-equivalence. In t cyclic s, two e zinc ato have o
eometry and the other two zinc ms ha igonal h
carboxylate groups. Other zinc atoms have coordination through a water molecule, one pyrazole, and three oxygen atoms of carboxylate. The crystal structure has two tetranuclear asymmetric molecules per unit cell. A slight difference in the tetranuclear units is revealed on careful analysis of the bond distances between the zinc atoms. In one metallacycle the
istances are Zn1−Zn1′, 11.561Å and Zn2−Zn2′, 12.642Å whereas in the other metallacycle d
these distances are Zn4−Zn4′, 11.559Å and Zn3−Zn3′, 13.095Å. From the bond distances between the zinc centers it is quite clear that the two void sizes are almost similar in the two asymmetric molecules. The important bond distances and angles of this complex are listed in Table 26 (Appendix).
Fig. 5.17 Two symmetry non-equivalent metallacycles in the unit cell of complex 5.10 (drawn to 30 % probability) [′= 2-x, -y, 1-z; ′′= 1-x, 2-y, -z]
It may be noted here that multiple voids with different sizes, in metal complex with one ligand, are not generally observed316. The structural study on such molecules may provide important information regarding understanding of high Z′ values335. In structure of the complex 5.10, two solvent molecules are in two different environments, this makes the two rings non symmetric with respect to crystallographic axis. The crystal structure of complex
A B
8 A) T f complex 5.11
5 that the dimethylformamide m re e l ugh 34
[dN2····O34 2.919 Å, <D−H····A 140.0º] and N8−H····O33 [dN8····O33 2.763 Å, <D−H····A 143.0º]
hermogram of complex 5.10, B) Thermogravimetric curve o Figure 5.1
.10 shows olecules a held in th attice thro N2−H····O
i py olec ydrogen bonded
w N4 3 Å ···A
N 1 Å, <D−H· º s t oor ater
m inte t late
o ck ed i 2.
T 5.10 s that ple eight
oordinated water molecules, one dimethylformamide and four pyrazole molecules in the lated lex loses 49.37% of its total weight which
lex
nteraction with pyrazole hydrogens. Remaining razole m ules are h
ith carboxylate oxygen through N4−H····O6 [d ····O6 2.75 , <D−H· 146.2º] and 6−H····O21 [dN6····O21 2.72 ···A 156.8 ]. Beside hat the c dinated w olecules are participate in O−H····O hydrogen bonding ractions wi h carboxy xygen. The hydrogen bonds contributing to the pa ing is list n Table 5.1
hermogravimetric analysis of the complex show the com x loses c
temperature range 100-240°C, which corresponds to 31.58% of the total weight (calcu weight loss 30.77%). In next step the comp
corresponds to the loss of one dicarboxylic acid molecule. The thermogravimetric curve of the comp 5.10 is shown in Figure 5.18A. The complex has IR absorptions at 1646 cm-1 and 1591cm-1 due to the C=O stretching frequency of dimethylformamide and carboxylate ligand respectively (Figure 5.27).
Table 5.12: Hydrogen bond geometry(Å, °) for complex 5.10
D−H···A d(D−H) d(H···A) d(D···A) <D−H···A N(2)−H(2)····O(34) 0.86 2.21 2.919(9) 140.0 N(4)−H(4A)····O(6) [ 2-x, -y, 1-z] 0.86 2.00 2.753(9) 146.2
−H(7B)····O(34) 0.69(8) 2.02(8) 2.713(8) 174.0(10) O(16)−H(16O)····O(21) [1-x,1-y, -z] 0.60(8) 2.15(8) 2.740(8) 166.9(7) O(16)−H(17O)····O(18) [1-x,1-y, -z] 0.93(9) 1.88(9) 2.743(8) 153.8(8) O(31)−H(31A)····O(33) [-1+x, y, z] 1.04(12) 1.79(12) 2.801(10) 161.4(10) O(31)-H(31B)····O(11) [-1+x, 1+y, z] 0.81(10) 2.03(10) 2.789(8) 155.5(9) N(6)−H(6A)····O(21) [1-x, 2-y, -z] 0.86 1.91 2.721(9) 156.8 N(8)−H(8A)····O(33) [-1+x, y, z] 0.86 2.03 2.763(12) 143.0 O(14)−H(7A)····O(27) [x, -1+y, z] 0.82 2.06 2.825(7) 155.6 O(14)
The co-ordination chemistry of (3-carboxymethoxy-naphthalen-2-yloxy)-acetic acid (L1H2) with zinc is extended to nitrogen containing bidentate ligands, such as 1,10-phenanthroline (Phen) and 2,2′-bipyridine (Bpy). In both the cases, mononuclear complexes 5.11 and 5.12 are obtained. In these complexes one of the carboxylate groups of the ligand co-ordinates and ther remains free in deprotonated form. Unfortunately, in both the complexes we are unabl maps. The complex
2 2
o e
to locate few hydrogen atoms of water molecules in the difference fourier
5.11 has a composition[Zn(L1)(Phen) ].3H O (where Phen is 1,10-phenanthroline) and has a
istorted octahedral geometry around zinc ion (Figure 5.19A) where two phenanthroline rings d
are cis to each other.
A B
Figure 5.19 A) Crystal structure of complex 5.11, B) Hydrogen bonded dimeric assembly of complex 5.11 (the hydrogen atom in oxygens could not be located) [′= 1-x, -y,-z; ′′= x, 1/2-y, -1/2+z; ′′′= 1-x, -1/2+y, 1/2-z]
The bidentate nature of 1,10-phenanthroline and the stabilization of free carboxylic acid group through hydrogen bonding prevent polymerization process. It is already reported that bulky bidentate ligands inhibits the co-ordination polymerization of dicarboxylates336. The water molecules are hydrogen bonded with the complex through O5····O9 [dO5····O9 2.995Å],
O9····O7 [dO9····O7 ] and O8····O1
[d 63Å] interactions to form ge ssem e
5 sembled in the lattice thr k 9 [d
Å ···O1 3.4 − .5º] ns.
S rogen bond paramete isted in Table 5.13. In the crystal structure of
th e phenanthroline rings is disor and i lved b ng the
o , C15-C24 atoms with 50% occupancy (T ).
ss of three water olecules and a 1,10-phenanthroline total weight loss is 28.82% (calculated weight loss is 31.03%). In the 1H NMR spectra the aromatic protons appear at 8.84, 8.69, 8.14, 7.83, 7.47, 7.24, 6.99ppm and the -CH2- protons appear at 4.35 ppm.
2.900Å], O7····O3 [dO7····O3 2.989Å], O6····O8 [dO6····O8 2.795Å
O8····O1 2.8 a hydro n bonded dimeric a bly (Figur
C28····O9 3.295 .19B).The complex is self as ough wea C28−H····O
, <D−H····A 169.5º] and C29−H· [dC29····O1 58 Å, <D H····A 159 interactio
ome important hyd rs are l
is molecule one of th dered t is reso y shari
ccupancy of the N1, N2 able 65
The FT-IR spectra of the complex 5.11 shows strong absorption at 1606 and 1420cm-1 due to asymmetric and symmetric C=O stretching of carboxylate. Thermogravimetric analysis shows that it loses three water molecules in the temperature range 50-120°C which corresponds to 6.31% of the total weight. The calculated loss is 7.16%. In the temperature range 210-290°C the complex loss one phenanthroline molecule (Figure 5.18B). Due to the lo
m
Table 5.13: Hydrogen bond geometry(Å, °)for complex 5.11
D−H···A d(D−H) d(H···A) d(D···A) <D−H···A C(28)−H(28)····O(9) [x, 1/2- y, 1/2+z] 0.93 2.38 3.295(15) 169.5 C(29)−H(29)····O(1) [x, 1/2- y, 1/2+z] 0.93 2.57 3.458(10) 159.5 C(36)−H(36)····O(8) [1+x,-1+y, z] 0.93 2.55 3.391(11) 150.4
1)(Bipy)2].7H2O (5.12) (where Bipy is 2,2′-bipyridine) is a mononuclear omplex with similar co-ordination feature as that of complex 5.11 (Figure 5.20A). The water The complex [Zn(L
c
molecules present in the lattice are assembled through O−H····O interactions. Two mononuclear complexes are self assembled in lattice through O5····O11 [dO5····O11 3.027Å], O11····O10 [dO11····O10 2.805Å], O5′····O10 [dO5′····O10 2.711Å] and O3····O11 [dO3····O11 2.927Å]
interactions which construct a hydrogen bonded hexameric unit as shown in Figure 5.20B.
A B
Figure 5.20 A) Crystal structure of complex 5.12 (the hydrogen atom in oxygens O8, O10,
could n 5.12
Besides that the water molecules are assem to m bonded
structure through O5·· 0 [d 2.711Å], O8····O10 [d 10 2.843Å], O8····O7 [d ····O7
2 O7····O5 ] s. atic
h ed in weak C28−H C28···· Å ···A
C , <D−H····A 148.2º] interactions bo xygen
a eters fo complex are listed in Table 5.14. The C=O
s he complex appea 632 c he zin es 2 with
,2′-bipyridine is mononuclear, whereas various dicarboxylic acids with bipyridine forms O11 and O12 ot be located); B) Hydrogen bonded hexameric structure of
bled ake a tetrameric hydrogen
··O1 O5····O10
.763Å], and O7−H····O5 [d 2.847
O8····O O8
The arom Å, <D−H····A 168.9º interaction
O7 3.275 , <D−H· 157.3º] and
ydrogens are involv ····O7 [d
34−H····O10 [dC34····O10 3.300 Å with car xylate o toms.. The hydrogen bond param r the
m-1. T c complex of L1H tretching frequency of t rs at 1
2
polymeric structures330.
Table 5.14: Hydrogen bond geometry(Å, °) for complex 5.12
D−H···A d(D−H) d(H···A) d(D···A) <D−H···A 0.73(7) 2.13(6) 2.847(6) 168.9(7) O(7)−H(7A)····O(5)
O(9)−H(9A)····O(6) [1+x, y, z] 0.75(7) 2.17(7) 2.877(6) 156.1(6) O(9)−H(9B)····O(8) 1.05(8) 2.13(8) 2.899(7) 128.4(5) C(28)−H(28)····O(7) [-x, 1-y, -z] 0.93 2.40 3.275(5) 157.3 C(34)−H(34)····O(10) 0.93 2.47 3.300(6) 148.2
The ligand L1H2 contains naphthalene ring, it has an electronic absorbance at 280 nm (ε = 1.1 X 10-5 mol-1 dm3cm-1); the fluorescence emission spectra of all the complexes were recorded by exciting at 290 nm in dimethylsulfoxide. In each case, we found emission at 327 nm and 342 nm (Figure 5.21). The emission intensity of the complexes is slightly lower than that of the parent acid. Although the changes are very nominal, the changes reflect the complexation of the ligand to the metal.
0 100 200 300 400 500 600 700 800 900
Intensity (a.u.)
LH2 complex 5.6 complex 5.7 complex 5.8 complex 5.9 complex 5.10 complex 5.11 complex 5.12
310 330 350 370 390 410 430 450
wave length (nm)
Figure 5.21 Fluorescence emission spectra of L1H2 and complexes 5.6-5.12
In conclusion the sodium complex of the 3-phenyl-2-(3-phenyl-ureido)-propionic acid (5.1) has anti-syn conformation around the urea moiety; whereas, in the manganese complex urea part adopts the conventional syn-syn conformation. It is also clear that polymorphism and symmetry non equivalence arise in (3-carboxymethoxy-naphthalen-2-yloxy) acetic acid (5.5
structures and stable packing geometry hich admits the different directional weak interactions. Depending on the type of ancillary ) and its derivative due to the differences in the layered structures or in the conformers. These differences arise from the favourable closed packed
w
ligands and reaction conditions (3-carboxymethoxy-naphthalen-2-yloxy)-acetic acid (5.5) forms varieties of zinc(II) complexes including coordination polymers. When cyclic zinc
a onodentate fashion. We have also shown example on occurrence of symmetry non- equivalent metallacycles in the unit cell. The symmetry non-equivalence in the complex arises from the location of the solvent molecules in the crystal lattice.