A novel blue luminescent material Na₂[Co(C₂O₄)₂(H₂O)₂]·6H₂O: synthesis, structure, luminescence and magnetic properties

Abstract

The synthesis, crystal structure and physical properties of new disodium trans-diaquabis(oxalato)cobaltate(ii)hexahydrate {Na2[Co(C2O4)2(H2O)2]·6H2O} crystals have been investigated. Single crystal X-ray analysis reveals that this compound crystallizes in the triclinic system with the space group P1[combining macron]. The structure of this complex consists of [Co(C2O4)2(H2O)2](2-) anionic units with a slightly distorted octahedral geometry of cobalt surrounded by four oxygen atoms of two oxalate groups. The anionic units are interlinked by two Na(+) ions with different octahedral and distorted octahedral environments. The electronic absorption spectra of the compound exhibit bands at 208, 246 and 526 nm in the UV and visible regions. A strong blue luminescence was observed at room temperature when excited at 355 nm. The M(H) curve at 2 K shows a significant nonlinear behaviour with almost zero coercivity which clearly indicates an extremely weak antiferromagnetic/ferromagnetic state of the complex.

Pyromellitate Ligand as Building Blocks in the Synthesis of Metal–Organic Frameworks with Hydroxyalkylamines

“…In the case of complex 6 , the maximum of this band is shifted to the UV region. Widened bands at 570 nm (complexes 4 and 5 ) and 519 nm (complex 6 ) in the visible region are related to metal d-d transition ( 4 T 1g (F) → 4 T 1g (P)), which is a characteristic of the high-spin octahedral environment of Co­(II) ion …”

“…Widened bands at 570 nm (complexes 4 and 5) and 519 nm (complex 6) in the visible region are related to metal d-d transition ( 4 T 1g (F) → 4 T 1g (P)), which is a characteristic of the high-spin octahedral environment of Co(II) ion. 61 In the UV−vis spectrum of Ni(II) complexes (Figure 4c), the bands at 319(8) nm and below relate, as in the spectra of Cu(II) and Co(II) complexes, to π−π* transitions within the aromatic rings of pyromellitate. The bands at 375 and 380 nm observed in spectra 8 and 9 are due to the charge transfer nitrogen−metal absorption band.…”

Synthesis, Structure, and Electrochemical Properties of Some Cobalt Oxalates

“…Our hydrothermal reactions in oxalate systems have resulted in five Co-based oxalate compounds, Na 2 Co 2 (C 2 O 4 ) 3 ·2H 2 O ( I ), Na 2 Co­(C 2 O 4 ) 2 ·8H 2 O ( II ), KLi 3 Co­(C 2 O 4 ) 3 ( III ), Li 4 Co­(C 2 O 4 ) 3 ( IV ), and (NH 4 ) 2 Co 2 (C 2 O 4 )­F 4 ( V ). Among them, I , II , and III are identical to previous literature structures, − and therefore they will not be described in detail (schematically illustrated in Figures S1–S3). Meanwhile, IV and V have not been reported elsewhere.…”

A Novel Copper Oxalate, Na2Cu(C2O4)2

“…Later, the magnetic properties of hydrothermally‐prepared Na 2 M 2 (C 2 O 4 ) 3 · 2H 2 O ( M = Fe, Co, Ni) and K 2 M (C 2 O 4 ) 2 ( M = Fe, Co) were studied . More recently, Hussain et al reported the photoemission of K 2 Ni(C 2 O 4 ) 2 · 6H 2 O and Na 2 Co(C 2 O 4 ) 2 · 8H 2 O, obtained by a slow evaporation method , . In all of these compounds, the transition metals (V, Fe, Co, Ni, Mo) are coordinated to six oxygen atoms of oxalate moieties and/or water molecules, forming distorted octahedra.…”

“…[7][8][9][10][11] More recently, Hussain et al reported the photoemission of K 2 Ni(C 2 O 4 ) 2 ·6H 2 O and Na 2 Co(C 2 O 4 ) 2 ·8H 2 O, obtained by a slow evaporation method. [12,13] In all of these compounds, the transition metals (V, Fe, Co, Ni, Mo) are coordi-106.948(9)°. The structure displays a novel stacking pattern of [Cu(C 2 O 4 ) 2 ] 2units connected through electrostatic attraction by Na + cations.…”