Elemental analyses contents (C, H and N) were determined at the Microanalytical Unit, Center of King Fahd Institute at Jeddah, Saudi Arabia. Copper and cobalt contents were determined by complexometric titration in the presence of Xylenol orange as an indicator [18] . Molar conductivities measurements were carried out using Tacussel model CD 75. The chloride and iodide contents were determined as AgCl or AgI [18] . The IR spectra in the 400 - 4000 cm⁻¹ range were recorded in KBr on a Mattson 5000 FTIR Spectrometer. The electronic spectra of the Cu²⁺ and Co²⁺ complexes were recorded in Nujol mull in the range (200 - 900 nm) using Unicam spectrometer model UV2. L was recorded on ¹H-NMR Spectrometer (400 MHz) in d₆-DMSO at Mansoura University at Mansoura. Magnetic moments were determined using a Sherwood balance at room temperature (25˚C) with Hg[Co(NSC)₄] as a calibrate. The diamagnetic corrections for L and its metal atoms were computed using Pascal’s constants [19] . The corrected values were calculated according to the following equation:

Χ d i a . ( molar ) = ∑ n A χ A + ∑ λ

where

χ_A = gram atomic susceptibility of atom A.

n_A = is the number of atom A in the compound.

λ = constitutive for certain bond types.

All the isolated metal complexes are colored, stable against light and air for two years. Also, the complexes are insoluble in most common organic solvents but easily soluble in DMF and DMSO. The molar conductivities for all the iodide complexes are non-conducting except the two complexes with the general formulae, [Cu(L)₃]I₂ and [Co(L)₃]I₂∙½EtOH∙2H₂O, which are conducting and have values 75 and 88 Ω⁻¹∙cm²∙mol⁻¹ in DMSO, respectively. On the other hand, the molar conductance of the chloride complexes in DMSO falls in the 55 - 75 Ω⁻¹∙cm²∙mol⁻¹ indicating 1:1 and 1:2 electrolytes, respectively. The low value (9 Ω⁻¹∙cm²∙mol⁻¹) for [Cu(L)Cl₂] indicates that the complex is non-electrolytic [20] . Moreover, the results show that the metal complexes have comparatively low melting points (168˚C - 254˚C) suggesting the weakness of the bond between the metal ions and L. The structure of L is represented as shown in Figure 1.

The IR spectrum of L in KBr (Figure S1) shows several bands at 3315, 3296 and 3131 cm⁻¹ assigned to ν_as(NH₂), ν_s(NH₂) and ν(NH) vibrations, respectively. The observation of broad weak bands in the 1940 - 1800 and 2755 - 2500 cm⁻¹ region suggests the presence of intra-molecular hydrogen bonding of the types O-H…..N and/or N-H….O [21] [22] . The bands observed at 1705 sh, 1635 sh and 1539s cm⁻¹ are assigned to ν(C=O), ν(NH₂) and ν(N-C-O) vibrations, respectively. The observation of the former two bands as shoulder bands suggests these

groups are taken part in hydrogen bonding. The results suggest that the first type of the hydrogen bonding (O-H…N) is more likely occurred. All these foundations suggest that L (MDH) can be represented in Figure 2.

The mode of bonding was determined by comparing the IR spectra of L with its complexes (Cu²⁺ and Co²⁺). The IR spectra of the complexes obtained by chemical method with the general formulae, [Cu(L)Cl₂] (Figure S2), [Co(L)₂(H₂O)Cl]Cl (Figure S3), [Cu(L)₃]Cl₂∙½EtOH (Figure S4) and [Co(L)₃]Cl₂ (Figure S5) indicate that the L behaves in a bidentate manner and coordinates via the two carbonyl groups forming six-membered ring around the metal ions. The negative shifts of these two bands to lower wavenumbers show the involvement of both these groups in bonding. The most important assignments IR bands for L and its metal complexes are listed in Table 1. Also, the ligand behaves in bidentate manner via the carbonyl oxygen (CO) and the amino (NH₂) groups in case of the complexes with the general formula, [M(L)₃]I₂∙XS (M = Cu²⁺, Co²⁺ and XS = zero in case of Cu²⁺ while XS = ½EtOH∙2H₂O in case of Co²⁺).

The ¹H-NMR spectrum of L in d₆-DMSO displays four signals at 10.3, 9.9, 9.3 and 3.9, relative to TMS (Figure 3). These signals are assigned to NH₂ (hydrogen-bonded), NH₂ (free), NH (free) and CH₂ protons, respectively. The results are taken as strong evidence for the existence of hydrogen bonding between CO and NH₂ groups and coincide with the results of IR spectra. The former three signals disappear on adding D₂O as shown in Figure S6.

The Cu²⁺ and Co²⁺ complexes with the general formulae, [Cu(L)Cl₂] (Figure S7), [Co(L)₂(H₂O)Cl]Cl (Figure S8), [Cu(L)₃]Cl₂∙½EtOH (Figure S9) and [Co(L)₃]Cl₂ (Figure S10), were carried out in Nujol mull. The spectrum of the Cu²⁺ complex,

[Cu(L)₃]Cl₂∙½EtOH, shows a band at 14368 cm⁻¹ attributed to ²E_g → ²T_2g transition [19] in a distorted-octahedral geometry around the Cu²⁺ ion. The value of magnetic moment is 2.0 BM is taken as additional evidence for the existence of distorted-octahedral geometry around the Cu²⁺ ion. On the other hand, the value of magnetic moment of the Co²⁺ complexes, [Co(L)₂Cl₂]Cl (5.2 BM) and [Co(L)₃]Cl₂ (4.9 BM) suggests the paramagnetic nature of the two complexes and the existence of d⁷-configuration around the Co²⁺ ion. Also, the data suggest that

no oxidation of Co²⁺ to Co³⁺ ion as reported earlier by Mostafa et al. [21] . The electronic spectrum of [Co(L)₂Cl₂]Cl in Nujol mull shows three bands in the 15,700, 19,840 and 21,740 - 28,900 cm⁻¹ regions attributed to the ³T_1g → ³T_2g, ³T_1g → ³A_2g and ³T_1g → ³T_1g transitions, respectively, in a high-spin octahedral Co²⁺ system. The observation of these three bands may also suggest that the complexes have trans-configuration [22] [23] . All the above foundations suggest representative structures for the isolated complexes with the general formulae, [Cu(L)Cl₂], [Co(L)(H₂O)₂Cl₂], [Co(L)₂(H₂O)Cl]Cl, [Cu(L)(H₂O)₂I₂] and [M(L)₃]I₂∙X (M = Cu²⁺ or Co²⁺; X = O in case for Cu²⁺ and X = ½EtOH∙2H₂O in case of Co²⁺ are shown in Figures 4-8, respectively.