Tris(2-(aminomethyl)pyridine)iron(II): a new spin-state equilibrium in solution

Chum, Helena L.; Vanin, J. A.; Holanda, Maria Isaura D.

doi:10.1021/ic00133a053

Cited by 51 publications

(19 citation statements)

References 6 publications

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“…A comparable effect was also noted in different salts of [Fe(3-bpp)2] 2+ (Scheme 2), whose SCO was shifted by up to 15 K higher temperature in the presence of more associating counterions, at NMR concentrations in a 9:1 (CD3)2CO:D2O solvent mixture [106]. While studies of [Fe(tacn)2] 2+ [99] or [Fe(pic)3] 2+ [100] reported no measurable response to different anions in solution, that might reflect the aqueous solvents used for those measurements, which would disfavor intermolecular hydrogen-bonding and ion pairing [107]. Although these results have yet to be addressed computationally, it is reasonable that formation of an N-H¨¨¨X hydrogen bond to an anion or solvent should increase the dipole on the N δ--H δ+ group.…”

Section: Effect Of Secondary Bonding Interactions On Metal Ion Spin Ssupporting

confidence: 60%

“…This has been best studied in a series of complexes [Fe(bip) 2 [100] reported no measurable response to different anions in solution, that might reflect the aqueous solvents used for those measurements, which would disfavor intermolecular hydrogen-bonding and ion pairing [107]. 2+ , since in that study both electron-donating and -withdrawing substituents led to a similar reduction in T½ [98].…”

Section: Effect Of Secondary Bonding Interactions On Metal Ion Spin Smentioning

confidence: 98%

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The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

2016

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Abstract:The relationship between chemical structure and spin state in a transition metal complex has an important bearing on mechanistic bioinorganic chemistry, catalysis by base metals, and the design of spin crossover materials. The latter provide an ideal testbed for this question, since small changes in spin state energetics can be easily detected from shifts in the spin crossover equilibrium temperature. Published structure-function relationships relating ligand design and spin state from the spin crossover literature give varied results. A sterically crowded ligand sphere favors the expanded metal-ligand bonds associated with the high-spin state. However, steric clashes at the molecular periphery can stabilize either the high-spin or the low-spin state in a predictable way, depending on their effect on ligand conformation. In the absence of steric influences, the picture is less clear since electron-withdrawing ligand substituents are reported to favor the low-spin or the high-spin state in different series of compounds. A recent study has shed light on this conundrum, showing that the electronic influence of a substituent on a coordinated metal ion depends on its position on the ligand framework. Finally, hydrogen bonding to complexes containing peripheral N-H groups consistently stabilizes the low-spin state, where this has been quantified.

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Section: Effect Of Secondary Bonding Interactions On Metal Ion Spin Ssupporting

confidence: 60%

Section: Effect Of Secondary Bonding Interactions On Metal Ion Spin Smentioning

confidence: 98%

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

2016

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“…Proton NMR measurements (Evans method) have been carried out to follow a temperature-dependent ST phenomenon in solution [82,112–117]. The paramagnetic peak changes position with varying temperature relative to a standard reference signal, which in favorable cases can be part of the SCO compound (e.g., the anion) [113–118], and this reflects the ST process.…”

Section: Reviewmentioning

confidence: 99%

Spin state switching in iron coordination compounds

Gütlich¹,

Gaspar²,

Garcia³

2013

Beilstein J. Org. Chem.

669

608

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SummaryThe article deals with coordination compounds of iron(II) that may exhibit thermally induced spin transition, known as spin crossover, depending on the nature of the coordinating ligand sphere. Spin transition in such compounds also occurs under pressure and irradiation with light. The spin states involved have different magnetic and optical properties suitable for their detection and characterization. Spin crossover compounds, though known for more than eight decades, have become most attractive in recent years and are extensively studied by chemists and physicists. The switching properties make such materials potential candidates for practical applications in thermal and pressure sensors as well as optical devices.The article begins with a brief description of the principle of molecular spin state switching using simple concepts of ligand field theory. Conditions to be fulfilled in order to observe spin crossover will be explained and general remarks regarding the chemical nature that is important for the occurrence of spin crossover will be made. A subsequent section describes the molecular consequences of spin crossover and the variety of physical techniques usually applied for their characterization. The effects of light irradiation (LIESST) and application of pressure are subjects of two separate sections. The major part of this account concentrates on selected spin crossover compounds of iron(II), with particular emphasis on the chemical and physical influences on the spin crossover behavior. The vast variety of compounds exhibiting this fascinating switching phenomenon encompasses mono-, oligo- and polynuclear iron(II) complexes and cages, polymeric 1D, 2D and 3D systems, nanomaterials, and polyfunctional materials that combine spin crossover with another physical or chemical property.

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“…The Fe II complexes 2a – c exhibit a large absorption band at 22600–23100 cm –1 with a weak low‐energy shoulder at 17400–18200 cm –1 . We assign the intense absorption to a metal‐to‐ligand charge‐transfer band (dπ→pπ*) typical of LS Fe II complexes with ‐acceptor ligands 19–22. This absorption appears to mask all d‐d transitions except the low‐energy shoulder that is generally assigned as the 1 A 1g → 1 T 1g transition in LS Fe II or Co III complexes 20,23…”

Section: Resultsmentioning

confidence: 99%

“…Additionally there is a very weak absorption at 11100–11800 cm –1 . This absorption is assigned to a 5 T 2g → 5 E g transition, as is seen in [Fe([12]aneN 3 py 3 )] 2+ and other HS Fe II complexes 19,20,22…”

Section: Resultsmentioning

confidence: 99%

Pyridine‐Ring Alkylation of Cytotoxic r‐1,c‐3,c‐5‐Tris[(2‐pyridylmethyl)amino]cyclohexane Chelators: Structural and Electronic Properties of the Mn^II, Fe^II, Ni^II, Cu^II and Zn^II Complexes

Childers

Przyborowska

et al. 2005

Eur J Inorg Chem

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. The cytotoxicities of the chelators toward human breast cancer cells (MCF7) at a fixed chelator concentration of 16 µM show time-dependent induction of cell death in the order tach-3-Mepyr ϾϷ tach-4-Mepyr Ͼ tach-5-Mepyr Ͼ tachpyr, whereas tach-6-Mepyr and tach-6-MeOpyr had no effect on the cells. The depressed cytotoxicities of the latter two are attributed to inability to bind Fe II or Zn II strongly.

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Tris(2-(aminomethyl)pyridine)iron(II): a new spin-state equilibrium in solution

Cited by 51 publications

References 6 publications

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

Spin state switching in iron coordination compounds

Pyridine‐Ring Alkylation of Cytotoxic r‐1,c‐3,c‐5‐Tris[(2‐pyridylmethyl)amino]cyclohexane Chelators: Structural and Electronic Properties of the Mn^II, Fe^II, Ni^II, Cu^II and Zn^II Complexes

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Tris(2-(aminomethyl)pyridine)iron(II): a new spin-state equilibrium in solution

Cited by 51 publications

References 6 publications

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

Spin state switching in iron coordination compounds

Pyridine‐Ring Alkylation of Cytotoxic r‐1,c‐3,c‐5‐Tris[(2‐pyridylmethyl)amino]cyclohexane Chelators: Structural and Electronic Properties of the MnII, FeII, NiII, CuII and ZnII Complexes

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Pyridine‐Ring Alkylation of Cytotoxic r‐1,c‐3,c‐5‐Tris[(2‐pyridylmethyl)amino]cyclohexane Chelators: Structural and Electronic Properties of the Mn^II, Fe^II, Ni^II, Cu^II and Zn^II Complexes