Chloride-induced assembly of manganese(II) complexes having oligomeric and chain structures

B. C Unni Nair, J. E. Sheats, R. Ponteciello, D. Van Engen, V. Petrouleas, G Charles Dismukes

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Abstract

The planar tridentate ligand 2,6-diacetylpyridine dioxime (H2dapd) forms complexes with Mn(II) having stoichiometries that are determined by the nature of the counterion. The monomeric bis chelate complex Mn(H2dapd)2X2 forms with outer-sphere counterions X = Br- (3) and ClO4 - (2). However, with Cl- a discrete oligomeric complex, [Mn(H2dapd)Cl2]n, probably dimeric (n = 2) or tetrameric (n = 4), forms in nonprotic solvents like DMF, while only a monomeric Mn(II) complex forms in protic solvents. This is in equilibrium with a linear-chain polymer n = ∞ (1) in the solid state. Compound 1 crystallizes in the monoclinic space group Cc [Z = 4, a = 17.843 (3) Å, b = 10.422 (2) Å, c = 6.809 (1) Å, β = 106.49 (0)°]. Mn coordinates to form pentagonal bipyramids Mn(N3Cl2)Cl2 in which each chloride occupies axial and equatorial sites on adjacent monomer units in the helical chains. Variable-temperature magnetic susceptibility indicates weak ferromagnetic coupling in 1 (μeff = 8.40 μB at 4.2 K and 6.02 μB at 294 K), with an effective spin-exchange temperature of T0 = 5 K (J = 0.2 cm-1), using a one-dimensional linear-chain classical model. This contrasts with the monomeric complex 2, which exhibits a temperature-independent moment 5.94-5.81 μB between 294 and 4.2 K, indicating no intermolecular coupling. The oligomeric complex of 1 in DMF also exhibits ferromagnetic coupling, as seen by the EPR-active paramagnetic ground state. Possible structures are discussed. The weaker ionic bonding between Mn(II) and Br- and ClO4 - vs Cl- accounts for the formation of the bis chelate complexes 2 and 3. The capacity for Cl- to spontaneously assemble an oligomeric Mn(II) cluster in solution is compared with the special requirement for Cl- for assembly of the polynuclear manganese complex responsible for photosynthetic water oxidation.

Original languageEnglish
Pages (from-to)1582-1587
Number of pages6
JournalInorganic Chemistry
Volume28
Issue number8
Publication statusPublished - 1989

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Manganese
manganese
Chlorides
assembly
chlorides
chelates
Photosynthetic Reaction Center Complex Proteins
spin exchange
Magnetic susceptibility
Stoichiometry
Temperature
Ground state
temperature
Paramagnetic resonance
stoichiometry
Polymers
monomers
Monomers
Ligands
solid state

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Nair, B. C. U., Sheats, J. E., Ponteciello, R., Van Engen, D., Petrouleas, V., & Dismukes, G. C. (1989). Chloride-induced assembly of manganese(II) complexes having oligomeric and chain structures. Inorganic Chemistry, 28(8), 1582-1587.

Chloride-induced assembly of manganese(II) complexes having oligomeric and chain structures. / Nair, B. C Unni; Sheats, J. E.; Ponteciello, R.; Van Engen, D.; Petrouleas, V.; Dismukes, G Charles.

In: Inorganic Chemistry, Vol. 28, No. 8, 1989, p. 1582-1587.

Research output: Contribution to journalArticle

Nair, BCU, Sheats, JE, Ponteciello, R, Van Engen, D, Petrouleas, V & Dismukes, GC 1989, 'Chloride-induced assembly of manganese(II) complexes having oligomeric and chain structures', Inorganic Chemistry, vol. 28, no. 8, pp. 1582-1587.
Nair BCU, Sheats JE, Ponteciello R, Van Engen D, Petrouleas V, Dismukes GC. Chloride-induced assembly of manganese(II) complexes having oligomeric and chain structures. Inorganic Chemistry. 1989;28(8):1582-1587.
Nair, B. C Unni ; Sheats, J. E. ; Ponteciello, R. ; Van Engen, D. ; Petrouleas, V. ; Dismukes, G Charles. / Chloride-induced assembly of manganese(II) complexes having oligomeric and chain structures. In: Inorganic Chemistry. 1989 ; Vol. 28, No. 8. pp. 1582-1587.
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abstract = "The planar tridentate ligand 2,6-diacetylpyridine dioxime (H2dapd) forms complexes with Mn(II) having stoichiometries that are determined by the nature of the counterion. The monomeric bis chelate complex Mn(H2dapd)2X2 forms with outer-sphere counterions X = Br- (3) and ClO4 - (2). However, with Cl- a discrete oligomeric complex, [Mn(H2dapd)Cl2]n, probably dimeric (n = 2) or tetrameric (n = 4), forms in nonprotic solvents like DMF, while only a monomeric Mn(II) complex forms in protic solvents. This is in equilibrium with a linear-chain polymer n = ∞ (1) in the solid state. Compound 1 crystallizes in the monoclinic space group Cc [Z = 4, a = 17.843 (3) {\AA}, b = 10.422 (2) {\AA}, c = 6.809 (1) {\AA}, β = 106.49 (0)°]. Mn coordinates to form pentagonal bipyramids Mn(N3Cl2)Cl2 in which each chloride occupies axial and equatorial sites on adjacent monomer units in the helical chains. Variable-temperature magnetic susceptibility indicates weak ferromagnetic coupling in 1 (μeff = 8.40 μB at 4.2 K and 6.02 μB at 294 K), with an effective spin-exchange temperature of T0 = 5 K (J = 0.2 cm-1), using a one-dimensional linear-chain classical model. This contrasts with the monomeric complex 2, which exhibits a temperature-independent moment 5.94-5.81 μB between 294 and 4.2 K, indicating no intermolecular coupling. The oligomeric complex of 1 in DMF also exhibits ferromagnetic coupling, as seen by the EPR-active paramagnetic ground state. Possible structures are discussed. The weaker ionic bonding between Mn(II) and Br- and ClO4 - vs Cl- accounts for the formation of the bis chelate complexes 2 and 3. The capacity for Cl- to spontaneously assemble an oligomeric Mn(II) cluster in solution is compared with the special requirement for Cl- for assembly of the polynuclear manganese complex responsible for photosynthetic water oxidation.",
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AU - Nair, B. C Unni

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AU - Dismukes, G Charles

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N2 - The planar tridentate ligand 2,6-diacetylpyridine dioxime (H2dapd) forms complexes with Mn(II) having stoichiometries that are determined by the nature of the counterion. The monomeric bis chelate complex Mn(H2dapd)2X2 forms with outer-sphere counterions X = Br- (3) and ClO4 - (2). However, with Cl- a discrete oligomeric complex, [Mn(H2dapd)Cl2]n, probably dimeric (n = 2) or tetrameric (n = 4), forms in nonprotic solvents like DMF, while only a monomeric Mn(II) complex forms in protic solvents. This is in equilibrium with a linear-chain polymer n = ∞ (1) in the solid state. Compound 1 crystallizes in the monoclinic space group Cc [Z = 4, a = 17.843 (3) Å, b = 10.422 (2) Å, c = 6.809 (1) Å, β = 106.49 (0)°]. Mn coordinates to form pentagonal bipyramids Mn(N3Cl2)Cl2 in which each chloride occupies axial and equatorial sites on adjacent monomer units in the helical chains. Variable-temperature magnetic susceptibility indicates weak ferromagnetic coupling in 1 (μeff = 8.40 μB at 4.2 K and 6.02 μB at 294 K), with an effective spin-exchange temperature of T0 = 5 K (J = 0.2 cm-1), using a one-dimensional linear-chain classical model. This contrasts with the monomeric complex 2, which exhibits a temperature-independent moment 5.94-5.81 μB between 294 and 4.2 K, indicating no intermolecular coupling. The oligomeric complex of 1 in DMF also exhibits ferromagnetic coupling, as seen by the EPR-active paramagnetic ground state. Possible structures are discussed. The weaker ionic bonding between Mn(II) and Br- and ClO4 - vs Cl- accounts for the formation of the bis chelate complexes 2 and 3. The capacity for Cl- to spontaneously assemble an oligomeric Mn(II) cluster in solution is compared with the special requirement for Cl- for assembly of the polynuclear manganese complex responsible for photosynthetic water oxidation.

AB - The planar tridentate ligand 2,6-diacetylpyridine dioxime (H2dapd) forms complexes with Mn(II) having stoichiometries that are determined by the nature of the counterion. The monomeric bis chelate complex Mn(H2dapd)2X2 forms with outer-sphere counterions X = Br- (3) and ClO4 - (2). However, with Cl- a discrete oligomeric complex, [Mn(H2dapd)Cl2]n, probably dimeric (n = 2) or tetrameric (n = 4), forms in nonprotic solvents like DMF, while only a monomeric Mn(II) complex forms in protic solvents. This is in equilibrium with a linear-chain polymer n = ∞ (1) in the solid state. Compound 1 crystallizes in the monoclinic space group Cc [Z = 4, a = 17.843 (3) Å, b = 10.422 (2) Å, c = 6.809 (1) Å, β = 106.49 (0)°]. Mn coordinates to form pentagonal bipyramids Mn(N3Cl2)Cl2 in which each chloride occupies axial and equatorial sites on adjacent monomer units in the helical chains. Variable-temperature magnetic susceptibility indicates weak ferromagnetic coupling in 1 (μeff = 8.40 μB at 4.2 K and 6.02 μB at 294 K), with an effective spin-exchange temperature of T0 = 5 K (J = 0.2 cm-1), using a one-dimensional linear-chain classical model. This contrasts with the monomeric complex 2, which exhibits a temperature-independent moment 5.94-5.81 μB between 294 and 4.2 K, indicating no intermolecular coupling. The oligomeric complex of 1 in DMF also exhibits ferromagnetic coupling, as seen by the EPR-active paramagnetic ground state. Possible structures are discussed. The weaker ionic bonding between Mn(II) and Br- and ClO4 - vs Cl- accounts for the formation of the bis chelate complexes 2 and 3. The capacity for Cl- to spontaneously assemble an oligomeric Mn(II) cluster in solution is compared with the special requirement for Cl- for assembly of the polynuclear manganese complex responsible for photosynthetic water oxidation.

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