Molecular structure and magnetic properties of copper(II), manganese(II) and iron(II) croconate tri-hydrate

Molecular properties of coordination compounds of the croconate ion with first-row sivalent transition metals: a quantum mechanical study

“…22,23 The magnetic properties of isostructural croconate complexes have been investigated in the last few years. 17,22 The observed magnetic moments of Mn 2+ (5.84), Fe 2+ (5.40), Co 2+ (5.11), Ni 2+ (3.26) and Cu 2+ (1.98 Bohr magnetons) indicate these compounds as high-spin complexes. 22 In addition to the interesting chemical physics aspects of these species that have motivated many studies, some nonlinear optical applications have also been reported.…”

“…Over the past years, the free oxocarbon ions as well as their coordination compounds have been widely studied concerning spectroscopic, 3-8 electromagnetic [9][10][11][12] and nonlinear optical properties. [13][14][15][16] Crystallographic structures of the squarate and croconate complexes with first-row transition metals have been described in the literature 9,[17][18][19][20][21][22] showing molecules with an infinite polymeric chain where the metal ions are surrounded by six oxygen atoms on a distorted octraedron. 17,18,22 The oxocarbon ion is usually chelated through oxygen atoms to one metal ion and singly-coordinated to another metal, leaving two of its five oxygen atoms (in the case of croconate) uncoordinated.…”

“…[13][14][15][16] Crystallographic structures of the squarate and croconate complexes with first-row transition metals have been described in the literature 9,[17][18][19][20][21][22] showing molecules with an infinite polymeric chain where the metal ions are surrounded by six oxygen atoms on a distorted octraedron. 17,18,22 The oxocarbon ion is usually chelated through oxygen atoms to one metal ion and singly-coordinated to another metal, leaving two of its five oxygen atoms (in the case of croconate) uncoordinated. The divalent croconate complexes with Mn 2+ , Fe 2+ , Cu 2+ , Ni 2+ , Co 2+ or Zn 2+ were found to be trihydrated with general formula M(C 5 O 5 )•3H 2 O and present similar powder X-ray diffraction patterns, differing only in the interplanar dspacing which is often associated to the π-stacking interactions.…”

Synthesis and characterization of cobalt(II) complexes of croconate and dicyanomethylene-substituted derivatives †

“…Though croconate (C 5 ) and rhodizonate (C 6 ) oxocarbons were first synthesized more than 170 years ago, 2 and copper() croconate was first reported by Gmelin in 1841, 3 their co-ordination chemistry remained poorly understood until the rebirth of the field following the discovery of squaric acid (C 4 ) in 1959. 4 Only a few structures of croconato complexes with first row transition-metal ions are known: [M(C 5 O 5 )(H 2 O) 3 ] (M = Cu II , Zn II , Mn II , Fe II ), [5][6][7] and also some complexes with croconate associated with another ligand such as imidazole, 8 histamine, 9 2,2Ј-bipyridine 10 or the bis(2-pyridylcarbonyl)amido anion. 11 Available structural data dealing with transition-metal croconate complexes show that this ligand can act either as a terminal (I) 8-10 or as a bridging ligand (II and III).…”

Poly[[[aqua(2,2′-bipyridine-κ2N,N′)manganese(II)]-μ-croconato-κ4O,O′:O′′,O′′′] monohydrate]: a one-dimensional coordination polymer connected by hydrophilic–hydrophilic and lipophilic–lipophilic interactions at 135 K

“…One or two croconate ligands can chelate in a bidentate manner a metal ion to form [M(C 5 O 5 )] (Brouca-Cabarrecq & Trombe, 1992a,b) or [M(C 5 O 5 ) 2 ] complexes (Chen et al, 2005). Various croconate-metal frameworks with three to five O atoms involved in coordination and bridging have also been formed (Glick & Dahl, 1966;Brouca-Cabarrecq & Trombe, 1992a,b;Cornia et al, 1993;Maji et al, 2003). We have previously reported several mixed-ligand complexes formulated as [M(C 5 O 5 )(phen) 2 ] (phen is 1,10phenanthroline).…”