Synthesis, Characterisation and Anti-Fungal Activities of Some New Copper(II) Complexes of Octamethyl Tetraaza-Cyclotetradecadiene

The ligand Me8[14]diene, L, in its free state as well as in the dihydroperchlorate form, L.2HClO4, coordinates copper(ll) in different salts to yield a series of [CuLXx] Xy(H2O)z complexes where X = NO3, ClO4, NCS, Cl and Br; x and y may have values of 0 or 2 and z = 0, 1 or 2. The complex, [CuL(ClO4)2].2H2O is found to undergo axial ligand substitution reactions with SCN-, NO3 and Cl- to give a variety of substitution derivatives: [CuL(ClO4)m Xn] where X = NCS, NO3 and Cl; m = 0 or 1, and n = 1 or 2. The complexes .have been characterised on the basis of analytical, spectroscopic, magnetic and conductance data. The anti-fungal activities of the ligand and its complexes have been investigated against a range of phytopathogenic fungi.

N HN NH N Template synthesis of four-coordinate square planar copper(ll) complexes of L has been achieved [1], but five-or six-coordinate copper(ll) complexes of this ligand have not been reported thus far. Owing to the steric hindrance of eight methyl groups in L, it was expected that the preparation of five-or six-coordinate complexes containing this ligand would be difficult. In one study, Bembi and coworkers [4] synthesised a number of six-coordinate cobalt(Ill) complexes [CoLXCl2](CIO4), where LX isomeric Me8114]anes; N-chiral isomers were separated and characterised. In another study [5], the preparation of six-coordinate dichlorocobalt(lll) complexes Vol. 6, No. 6,1999 Synthesis, Characterisation and Anti-fungal Activities of some New Copper (II) Complexes of L was achieved. Subsequently, in an recent study, Hazari et al. [6] were successful in preparing some six-coordinate copper(ll) complexes containing the saturated isomeric M% [14]anes analogues of L, [Cu(Me [14]anes)X2] n/ (where X NO 3, H20, CI and Br; n 0, or 2). Hence, it seemed likely that higher coordination number copper(ll) complexes could also be prepared with L. In this context, a number of fourand six-coordinate copper(ll) complexes have been isolated and their anti-fungal activities, as well as those of L, investigated.

Experimental 1 Synthesis
The dihydroperchlorate salt of the ligand, 3,10-C-meso-Me8114]diene.2HCIO4, hereafter L. 2HCIO 4, was synthesised according to the literature method [1]. The free ligand, 3,10-C-meso-Mee [14]diene, L, was obtained by extracting the ligand with chloroform from a suspension of L.2HCIO4in water at apH above 12 After separating the green product, the mother liquor was further heated for 30 min during which time the solution turned a violet colour and finally evaporated. The dry product was extracted with CHCI 3. The CHCI 3 extract was then evaporated to dryness to yield a violet product, [CuLBr2].2H20; dec. pt 240C. Found N, 9.81; Cu, 11.17 %. 018H40CuBr2N402 requires N, 9.87; Cu, 11.19%.
The above violet product, on exposure to air at room temperature, produced a pink product, [CuL]Br2.2H20; dec. pt 240C. Found N, 9.82; Cu, 11.17 %. 018H4oBr2CuN402 requires N, 9.87; Cu, 11.19 %. The pink product on heating to 70 80C reverts to the violet product.

2 Physical measurements
Visible spectra were recorded on a Shimadzu UV-visible spectrophotometer. The mass spectrum was measured at the Department of Radiochemistry and Biophysics, Nigata College of Pharmacy, Nigata, Japan. Conductance measurements were carried out on a conductivity bridge model Hanna Instruments HI-8820 at 25 + 0o1C. Magnetic measurements were made on Gouy Balance which was calibrated using Hg[Co(NCS)4]. IR spectra were recorded on a Perkin-Elmer model-883 infrared spectrophotometer as KBr disks.

3 Elemental analysis
For the analysis of nitrogen, Kjeldahl's method, for copper standard titrimetric methods, and for sulphur standard gravimetric methods have been employed.

Anti-fungal activities
The actifungal activities of L.2HCIO4, and its copper complexes (in vitro) against some selected phytopathogenic fungi were assessed by the poisoned food technique. Potato Dextrose Agar (PDA) was used as a growth medium. DMF was used as the solvent, initially to prepare solutions of the compounds. The solutions were then mixed with the sterilised PDA to maintain the concentration of the compounds at 0.01%; 20 ml of these were each poured into a petri dish. After the medium had solidified, a 5 mm mycelial disc for each fungus was placed in the centre of each .2H20 for which a single crystal structure analysis has been undertaken and reported elsewhere [7]. It is assumed that the stereochemistries of the substitution products remain the same as the parent compound. Characterisation of the complexes could be achieved by IR and UV/VIS spectroscopic data as well as by magnetochemical and conductance measurements. Physical and spectroscopic data are presented in Tables and 2.
An examination of molecular models show that owing to the presence of two chiral N-centres in L, up to four diastereoisomeric complexes of the same geometry may result. Out of these possibilities, all are not stable in solid state. In this study, only one diastereoisomer of each complex was isolated.

3.1
Copper(ll) diperchiorato complex The interaction of copper(ll) chloride with L.2HCIO 4 yields a reddish pink product, [CuL(CIO4)2].2H20. The same product could also be prepared by the reaction of L.2HCIO 4 with Cu(CIO4)2.6H20 as well as with Cu(NO3)2.3H20 as demonstrated by infrared spectroscopy.
The IR spectrum exhibits bands at 1130, 1080, 915 and 620 cm 1 due to the perchlorate group. The splitting of a band at 1100 cm 4 into 1130 cm and 1080 cm is an indication of presence of coordinated perchlorate and the position of the bands strongly supports a unidentate mode of coordination [8]. Presence of a YON band at 3420 cm 1 and a aoa band at 1650 cm overlapping with a VCN band are attributed to the presence of lattice water [9]. The spectrum further shows the appearance of bands due to C=N, NH, C-C, CH3 in the expected regions. Selected IR bands for all complexes are collected in Table 1. The conductance value at 0.0 ohm cm 2 mol (Table 2) for this complex in CHCI 3 solution is an indication of the non-electrolytic nature of the complex, i.e. both CIO 4 groups are in the coordination sphere. This assignment, i.e. an octahedral geometry, has been confirmed by an X-ray structure determination [7]. However, in DMF and water where the colour is changed to pink-violet and pink, respectively, the conductance values corresponding to 1:2 electrolytes indicate that solvent molecules replace perchlorate in the coordination sphere as has been noted in related systems [6]. It is possible that in case of DMF, being relatively large molecule, two molecules may not enter the coordination sphere but rather they may force the anions out of the sphere to form a square planar complex, [CuL](CIO4) 2 as has been observed in analogous complexes [10].
It has been shown that copper(ll) centres in macrocycles generally have square planar or tetragonally distorted octahedral geometries and that these give rise to broad bands in the visible region due to overlap of Alg ---> Big, B2g ----> Big and Eg ----> Big transitions [10]. However, the molar conductivity value in pink-violet DMF solution corresponding to a 1:1 electrolyte may be accounted for by the replacement of weakly bound CIO 4 by DMF or by the presence of an equilibrium mixture of octahedral [CuLCI(CIO4) and square planar [CuL]CI(CIO4). Further, the conductance value (190 ohm cm 2 mol) of pink aqueous solution corresponding to a 1:2 electrolyte clearly suggests that the anions are replaced by H20 molecules [6] as described earlier. The magnetic moment and electronic data are consistent with an originally tetragonally distorted octahedral structure. It has been concluded that once the octahedral complex is formed, substitution of the axial ligands takes place without change of conformation as established in the case of cobalt(Ill) complexes containing the same ligand [11]. In the IR spectrum of the complex, a band at 1380 cm , similar to that found in the spectrum of free ligand can be assigned to absorptions due to CH 3 groups [12]. A medium band at 1300 cm 1 and a shoulder at 1410 cm , that overlapped with the band due to methyl groups, are attributed to coordinated nitrate group. The separation of these bands by 110 cmand the appearance of a single sharp M-O band at 320 cm is indicative of unidentate nitrate [13]. The spectrum further shows the bands at 1125, 1080, 940 and 620 cm which can be safely assigned to the presence of a unidentate perchlorate group. The conductance value (0.0 ohm cm 2 mol) of a reddish-pink CHCI 3 solution of this complex is indicative of the non-electrolytic nature of the complex, i.e. nitrate and perchlorate are in the coordination sphere. However, the molar conductivity (94 ohm cm 2 mol ) in DMF corresponds to a 1"1 electrolyte and is attributed to an equilibrium between octahedral [CuL(NO3)(CIO4) and square planar [CuL](NO3)(CIO4) [10]. The electronic spectral and magnetic data, Table 2, are consistent with the tetragonally distorted octahedral structure. 3.4 Copper(ll) diisothiocyanato complex [CuL(CIO4)2].2H20 was reacted with KSCN in the ratio of 1:2 in methanol solution to produce a mixture of white and violet products. This mixture was extracted with chloroform which on evaporation yielded a violet product, characterised as [CuL(NCS)2].
In the IR spectrum of [CuL(NCS)2], the appearance of distinct, sharp VCN at 2025 cm , Vcs at 820 cm and VNcsat 470 cm bands is a good indication of the coordination of NCS ions and their positions fully supports the N bonded thiocyanate group [13]. This assignment is in good agreement with the fact that generally first row transition metal complexes of thiocyanate form M-N bonds [13]. Absence of bands at around 1100 cm1, 920 cm 1 and 625 cm in this complex reveals that although this complex has been prepared from a diperchlorato precursor, the perchlorate ions are fully replaced by thiocyanate ions.
The molar conductivity value of 0.00 ohm cm 2 mol of this complex in chloroform solution strongly supports the non-electrolytic nature of the complex, i.e. both thiocyanate ions are in the coordination sphere. The conductance value in DMF solution, corresponding to an 1:1 electrolyte, can be explained in terms of the phenomena discussed above (Section 3.3). 3.5 Copper(ll) nitrate complexes The interaction of free ligand L with copper(ll) nitrate in the ratio of 1:2 in methanol solution yielded one green fraction immediately and a violet product later. The green product was found to be insoluble in almost all solvents and the quantity isolated was insufficient for full characterisation.
The IR spectrum of the green product reveals a sharp, intense band at 1375 cm that may be attributed to ionic, non-coordinating NO 3 and methyl groups [12]. The spectrum further shows all of some New Copper (II) Complexes the characteristic bands as observed for the free ligand. From these data it is proposed that the complex may have a square planar geometry of molecular formula [CuL](NO3) 2. The IR spectrum of violet [CuL(NO3)2].H20 exhibits a band at 1380 cm which may be due to the CH 3 groups. Presence of two bands at 1435 cm and 1325 cm are attributed to nitrate groups. The separation of the bands by 110 cm and a single M-O stretching band at 250 cm are indications of coordinated unidentate nitrate groups [13]. The presence of lattice water is indicated by the presence of bands at 3440 cm and 1625 cm [9]. The conductance value of 0.0 ohm cm 2 mol in chloroform solution shows that the complex is essentially a non-electrolyte. However, in DMF and water, the molar conductivity values indicate that this complex behaves as an 1 [CuL]Br2.2H20 and violet [CuLBr2].2H20. The green product was isolated in insufficient quantity to be characterised fully. The same type of green product was also obtained during the reaction of L with copper(ll) nitrate for which a square planar geometry was proposed. Both of these green products are expected to be the same diastereoisomer. The pink product was obtained at room temperature and the violet product can be isolated in the absence of moisture or by heating the pink product to 70-80C. Moreover, the violet product reverts to the pink one on exposure to  (Table 2)indicate normal behaviour for these d e systems. This study demonstrates that it is possible to form tetragonally distorted octahedral copper(ll) complexes with the sterically congested macrocycle with eight peripheral methyl groups, L. Since the two methyl groups of the chiral carbon atoms and the two methyl groups at C=N are equatorially orientated in L, the participation of weakly-coordinating, relatively large ions such as perchlorate in the coordination sphere is allowed. Small and labile ligands such as Br was found to have facile entrance and exit in the coordination sphere.
Fungitoxicity study The anti-fungal activities of the ligand and some of its complexes are summarised in Table 3. Screens have been conducted against three selected phytopathogenic fungi: i) Altemaria altemata, ii) Curvularia lunata, and iii) Macrophomina phaseolina. The activities of the free ligand and its complexes against Macrophomina phaseolina are generally greater than those against the other two fungi. This is in contrast to that observed in case of its saturated isomeric macrocycles Me8114]anes and their copper(ll) complexes [6], where the activities were greater against Altemaria altemata than those against other two fungi. This observation suggests that the diene ligand may have a different effect on these organisms. The activities of this ligand were found to decrease upon coordination to copper(ll), as usual.
The fungitoxicities are generally lower than those of related sulphur containing Schiff bases and their complexes [14]. It is noteworthy that the decrease in activity upon coordination of this particular ligand was found to be less compared to that of sulphur containing compounds [14] but comparable to that observed in case of its saturated macrocyclic analogues [6].