Synthesis and spectral characterization of zinc(II), copper(II), nickel(II) and manganese(II) complexes derived from bis(2-hydroxy-1-naphthaldehyde) malonoyldihydrazone

Abstract

The present study shows that the reaction of different salts of the same metal with sterically crowded dihydrazone bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone (CH 2 LH 4 ) in ethanol/aqueous media gives complexes of different stereochemistry. While the reaction of zinc(II) and copper(II) sulphate with dihydrazone yields tetrahedral complexes, the zinc(II) and copper(II) chlorides give square pyramidal and distorted octahedral complexes, respectively. On the other hand, nickel(II) sulphate and chloride, both give high-spin octahedral complexes with dihydrazone, manganese sulphate gives low-spin octahedral and manganese(II) chloride gives high-spin octahedral complexes. The reaction of these complexes with KF has been investigated. All of the products have been characterized by analytical, magnetic moment and molar conductivity data. The structures of the complexes have been established by spectroscopic studies.

Synthesis, and characterization of low- and high-spin manganese(II) complexes of polyfunctional adipoyldihydrazone: Effect of coordination of N-donor ligands on stereo-redox chemistry

“…Usually high-spin Mn(II) complexes rarely show d-d transitions. However, the complexes show low intensity peaks around 455-483 nm corresponding to 6 A 1g (F) -4 T 2g (G) transitions, as has been reported for Mn(II) octahedral complexes [11,21,24].…”

“…The band at 290 nm is assigned to intraligand p-p ⁄ transitions while the bands in the region 313-363 nm are assigned to n-p ⁄ transitions. The bands in the region 313-363 nm are characteristic of the napthaldimine part of ligand as has been reported in several monoacyl hydrazones [11,20,21]. The last two bands in npahH 4 are split into two components, each in the complexes.…”

“…for complex (1) suggests that it is a low-spin complex. Very few low-spin complexes of di-and tri-valent manganese are currently known [6][7][8][9][10][11][17][18][19]. Although the complex (1) should show l B value corresponding to one unpaired electron, considering orbital contribution, the l B value exhibited by the complex (1) should fall around ca.…”

“…These appear to have contributions from ligand band at 363 nm which is, most probably, red shifted in complexes and as well as from charge transfer bands arising due to charge transfer from naphtholate oxygen atoms to metal center [11,21]. The d-d transitions in the Mn(II) complexes are very weak because they are both spin as well as laporte forbidden [22].…”

“…Low-spin Mn(II) complexes have been known with cyano ligands [6,17], phosphine ligands [7], oxime ligands [8,19], and dithiochelate ligands [9]. Recently, a few low-spin manganese(II) complexes have been reported by various groups [10], and also by us in our earlier reported work with ligand bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone [11]. The lower oxidation state species of manganese(II) are commonly 6-coordinate.…”