Syntheses and characterization of iron(II) and iron(III) complexes of a tripodal ligand derived from tris(2-aminoethyl)methane

Greg Brewer, Cynthia Brewer, Genevieve White, Ray J. Butcher, Carol Viragh, Everett E. Carpenter, Ann Marie Schmiedekamp

Research output: Contribution to journalArticle

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Abstract

The trihydrochloride salt of tris(2-aminoethyl)methane (tram·3HCl) was deprotonated in methanolic potassium hydroxide and reacted with three molar equivalents of imidazole-2-carboxaldehyde to give a new Schiff base ligand, HC(CH2CH2N{double bond, long}CH-2ImH)3. The ligand, H3(1), was reacted in situ with iron(II)chloride tetrahydrate. Addition of excess sodium perchlorate resulted in the isolation of the dark red [FeH3(1)](ClO4)2·KClO4. The neutral emerald green iron(III) tripodal complex, Fe(1), was prepared by the aerial oxidation of the iron (II) complex on addition of three equivalents of potassium hydroxide. The complexes are characterized by EA, IR, ESI-MS, Mössbauer, magnetic susceptibility and single crystal XRD. The spectroscopic and structural data support a low spin assignment for both the iron(II) and iron(III) complexes at 295 K. The overall conformation of the tram backbone in these complexes has the apical carbon atom, Cap, pointed away from the iron atom with an average non-bonded distance of 3.83 Å. However, Cap is distorted from tetrahedral geometry toward trigonal monopyramidal. This is indicated by a narrowing of the H-Cap-C angles, an expansion of the C-Cap-C angles and a compression along the C-H axis so that Cap approaches the plane defined by its three carbon substituents. Two unusual supramolecular features are exhibited in [FeH3(1)](ClO4)2·KClO4. These are a polymeric [K(ClO4)32-]n anion and a bidentate hydrogen bonding donor, Nimine{double bond, long}CH-Cimidazole-NimidazoleH, on each arm of the tripodal ligand. Density Functional Theory (DFT) calculations using the B3LYP functional were performed on the low spin and high spin states of both complexes. B3LYP correctly predicts that the low spin state is favored in both systems and closely matches the important metrical parameters that are indicative of spin state. B3LYP shows that the Cap-out conformation of the tram backbone would be nearly identical in the low and high spin forms.

Original languageEnglish (US)
Pages (from-to)4158-4166
Number of pages9
JournalInorganica Chimica Acta
Volume362
Issue number11
DOIs
StatePublished - Aug 15 2009

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Methane
caps
methane
Iron
Ligands
iron
ligands
synthesis
potassium hydroxides
Potassium hydroxide
Conformations
Carbon
methylidyne
beryl
Atoms
Schiff Bases
carbon
Chemical bonds
perchlorates
Magnetic susceptibility

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

Cite this

Brewer, Greg ; Brewer, Cynthia ; White, Genevieve ; Butcher, Ray J. ; Viragh, Carol ; Carpenter, Everett E. ; Schmiedekamp, Ann Marie. / Syntheses and characterization of iron(II) and iron(III) complexes of a tripodal ligand derived from tris(2-aminoethyl)methane. In: Inorganica Chimica Acta. 2009 ; Vol. 362, No. 11. pp. 4158-4166.
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abstract = "The trihydrochloride salt of tris(2-aminoethyl)methane (tram·3HCl) was deprotonated in methanolic potassium hydroxide and reacted with three molar equivalents of imidazole-2-carboxaldehyde to give a new Schiff base ligand, HC(CH2CH2N{double bond, long}CH-2ImH)3. The ligand, H3(1), was reacted in situ with iron(II)chloride tetrahydrate. Addition of excess sodium perchlorate resulted in the isolation of the dark red [FeH3(1)](ClO4)2·KClO4. The neutral emerald green iron(III) tripodal complex, Fe(1), was prepared by the aerial oxidation of the iron (II) complex on addition of three equivalents of potassium hydroxide. The complexes are characterized by EA, IR, ESI-MS, M{\"o}ssbauer, magnetic susceptibility and single crystal XRD. The spectroscopic and structural data support a low spin assignment for both the iron(II) and iron(III) complexes at 295 K. The overall conformation of the tram backbone in these complexes has the apical carbon atom, Cap, pointed away from the iron atom with an average non-bonded distance of 3.83 {\AA}. However, Cap is distorted from tetrahedral geometry toward trigonal monopyramidal. This is indicated by a narrowing of the H-Cap-C angles, an expansion of the C-Cap-C angles and a compression along the C-H axis so that Cap approaches the plane defined by its three carbon substituents. Two unusual supramolecular features are exhibited in [FeH3(1)](ClO4)2·KClO4. These are a polymeric [K(ClO4)32-]n anion and a bidentate hydrogen bonding donor, Nimine{double bond, long}CH-Cimidazole-NimidazoleH, on each arm of the tripodal ligand. Density Functional Theory (DFT) calculations using the B3LYP functional were performed on the low spin and high spin states of both complexes. B3LYP correctly predicts that the low spin state is favored in both systems and closely matches the important metrical parameters that are indicative of spin state. B3LYP shows that the Cap-out conformation of the tram backbone would be nearly identical in the low and high spin forms.",
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Syntheses and characterization of iron(II) and iron(III) complexes of a tripodal ligand derived from tris(2-aminoethyl)methane. / Brewer, Greg; Brewer, Cynthia; White, Genevieve; Butcher, Ray J.; Viragh, Carol; Carpenter, Everett E.; Schmiedekamp, Ann Marie.

In: Inorganica Chimica Acta, Vol. 362, No. 11, 15.08.2009, p. 4158-4166.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Syntheses and characterization of iron(II) and iron(III) complexes of a tripodal ligand derived from tris(2-aminoethyl)methane

AU - Brewer, Greg

AU - Brewer, Cynthia

AU - White, Genevieve

AU - Butcher, Ray J.

AU - Viragh, Carol

AU - Carpenter, Everett E.

AU - Schmiedekamp, Ann Marie

PY - 2009/8/15

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N2 - The trihydrochloride salt of tris(2-aminoethyl)methane (tram·3HCl) was deprotonated in methanolic potassium hydroxide and reacted with three molar equivalents of imidazole-2-carboxaldehyde to give a new Schiff base ligand, HC(CH2CH2N{double bond, long}CH-2ImH)3. The ligand, H3(1), was reacted in situ with iron(II)chloride tetrahydrate. Addition of excess sodium perchlorate resulted in the isolation of the dark red [FeH3(1)](ClO4)2·KClO4. The neutral emerald green iron(III) tripodal complex, Fe(1), was prepared by the aerial oxidation of the iron (II) complex on addition of three equivalents of potassium hydroxide. The complexes are characterized by EA, IR, ESI-MS, Mössbauer, magnetic susceptibility and single crystal XRD. The spectroscopic and structural data support a low spin assignment for both the iron(II) and iron(III) complexes at 295 K. The overall conformation of the tram backbone in these complexes has the apical carbon atom, Cap, pointed away from the iron atom with an average non-bonded distance of 3.83 Å. However, Cap is distorted from tetrahedral geometry toward trigonal monopyramidal. This is indicated by a narrowing of the H-Cap-C angles, an expansion of the C-Cap-C angles and a compression along the C-H axis so that Cap approaches the plane defined by its three carbon substituents. Two unusual supramolecular features are exhibited in [FeH3(1)](ClO4)2·KClO4. These are a polymeric [K(ClO4)32-]n anion and a bidentate hydrogen bonding donor, Nimine{double bond, long}CH-Cimidazole-NimidazoleH, on each arm of the tripodal ligand. Density Functional Theory (DFT) calculations using the B3LYP functional were performed on the low spin and high spin states of both complexes. B3LYP correctly predicts that the low spin state is favored in both systems and closely matches the important metrical parameters that are indicative of spin state. B3LYP shows that the Cap-out conformation of the tram backbone would be nearly identical in the low and high spin forms.

AB - The trihydrochloride salt of tris(2-aminoethyl)methane (tram·3HCl) was deprotonated in methanolic potassium hydroxide and reacted with three molar equivalents of imidazole-2-carboxaldehyde to give a new Schiff base ligand, HC(CH2CH2N{double bond, long}CH-2ImH)3. The ligand, H3(1), was reacted in situ with iron(II)chloride tetrahydrate. Addition of excess sodium perchlorate resulted in the isolation of the dark red [FeH3(1)](ClO4)2·KClO4. The neutral emerald green iron(III) tripodal complex, Fe(1), was prepared by the aerial oxidation of the iron (II) complex on addition of three equivalents of potassium hydroxide. The complexes are characterized by EA, IR, ESI-MS, Mössbauer, magnetic susceptibility and single crystal XRD. The spectroscopic and structural data support a low spin assignment for both the iron(II) and iron(III) complexes at 295 K. The overall conformation of the tram backbone in these complexes has the apical carbon atom, Cap, pointed away from the iron atom with an average non-bonded distance of 3.83 Å. However, Cap is distorted from tetrahedral geometry toward trigonal monopyramidal. This is indicated by a narrowing of the H-Cap-C angles, an expansion of the C-Cap-C angles and a compression along the C-H axis so that Cap approaches the plane defined by its three carbon substituents. Two unusual supramolecular features are exhibited in [FeH3(1)](ClO4)2·KClO4. These are a polymeric [K(ClO4)32-]n anion and a bidentate hydrogen bonding donor, Nimine{double bond, long}CH-Cimidazole-NimidazoleH, on each arm of the tripodal ligand. Density Functional Theory (DFT) calculations using the B3LYP functional were performed on the low spin and high spin states of both complexes. B3LYP correctly predicts that the low spin state is favored in both systems and closely matches the important metrical parameters that are indicative of spin state. B3LYP shows that the Cap-out conformation of the tram backbone would be nearly identical in the low and high spin forms.

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