Filling the Gap in Extended Metal Atom Chains: Ferromagnetic Interactions in a Tetrairon(II) String Supported by Oligo-α-pyridylamido Ligands.
Alessio NicoliniRita GalavottiAnne-Laure BarraMarco BorsariMatteo CaleffiGuangpu LuoGhenadie NovitchiKyungwha ParkAntonio RanieriLuca RigamontiFabrizio RoncagliaCyrille TrainAndrea CorniaPublished in: Inorganic chemistry (2018)
The stringlike complex [Fe4(tpda)3Cl2] (2; H2tpda = N2, N6-bis(pyridin-2-yl)pyridine-2,6-diamine) was obtained as the first homometallic extended metal atom chain based on iron(II) and oligo-α-pyridylamido ligands. The synthesis was performed under strictly anaerobic and anhydrous conditions using dimesityliron, [Fe2(Mes)4] (1; HMes = mesitylene), as both an iron source and a deprotonating agent for H2tpda. The four lined-up iron(II) ions in the structure of 2 (Fe···Fe = 2.94-2.99 Å, Fe···Fe···Fe = 171.7-168.8°) are wrapped by three doubly deprotonated twisted ligands, and the chain is capped at its termini by two chloride ions. The spectroscopic and electronic properties of 2 were investigated in dichloromethane by UV-vis-NIR absorption spectroscopy, 1H NMR spectroscopy, and cyclic voltammetry. The electrochemical measurements showed four fully resolved, quasi-reversible one-electron-redox processes, implying that 2 can adopt five oxidation states in a potential window of only 0.8 V. Direct current (dc) magnetic measurements indicate dominant ferromagnetic coupling at room temperature, although the ground state is only weakly magnetic. On the basis of density functional theory and angular overlap model calculations, this magnetic behavior was explained as being due to two pairs of ferromagnetically coupled iron(II) ions ( J = -21 cm-1 using JŜ i·Ŝ j convention) weakly antiferromagnetically coupled with each other. Alternating-current susceptibility data in the presence of a 2 kOe dc field and at frequencies up to 1.5 kHz revealed the onset of slow magnetic relaxation below 2.8 K, with the estimated energy barrier Ueff/ kB = 10.1(1.3) K.
Keyphrases
- room temperature
- aqueous solution
- density functional theory
- molecularly imprinted
- molecular dynamics
- metal organic framework
- ionic liquid
- visible light
- electron transfer
- quantum dots
- gold nanoparticles
- iron deficiency
- wastewater treatment
- high resolution
- molecular docking
- risk assessment
- nitric oxide
- molecular dynamics simulations
- machine learning
- drug delivery
- high frequency
- drug release
- heavy metals
- fluorescence imaging