Azomethine Fe³⁺ coordination compounds containing carbazole units: Synthetic approach, spectral characterization, and magnetic studies

Abstract

The main aim of our study is to investigate various types of hybrid systems with a paramagnetic iron (III) ion as a core and photoactive derivatives of carbazole at the periphery. We have synthesized a variety of biligand coordination compounds with the composition [FeL2]A (where L is 2‐[2‐[(E)‐[4‐[4‐(3,6‐di‐tert‐butylcarbazol‐9‐yl)benzoyl]oxy‐2‐phenolate]methyleneamino]ethylamino]ethyl 4‐(3,6‐di‐tert‐butylcarbazol‐9‐yl)benzoate, A− is NO3− (I), Cl− (II), PF6− (III)). These systems were studied by superconducting quantum interference device (SQUID) magnetometry and X‐band electron paramagnetic resonance (EPR) spectroscopy. Magnetic measurements revealed mixed spin states (high spin [HS], low spin [LS]) of Fe (III) ions at room temperatures. Estimates of the corresponding spin contributions were made. It was found that all samples exhibit AFM exchange interactions between iron (III) ions. The ground spin state at 2.0 K was established and analyzed. EPR measurements confirmed the HS states of iron (III) and revealed two types of them: with weak distorted and strong low‐symmetry octahedral crystal fields.

New Branched Iron(III) Complexes in Fluorescent Environment Created by Carbazole Moieties: Synthesis and Structure, Static Magnetic and Resonance Properties

“…The triplet signal of the amino group of Di(CrB)amine (4.49-4.46 All three complexes are paramagnetic, as evidenced by the broadened signals in the 1 H NMR spectra, which do not allow a clear determination of the structure of the compounds. This broadening of spectral response is typical for the paramagnetic Fe 3+ ion in an azomethine environment [12,19]. In this case, the signal width in the spectrum consists of its own, determined by the relaxation time and associated with the inhomogeneity of the magnetic field.…”

“…We continue to study a new series of Fe 3+ dendrimeric complexes. This work is a logical continuation of our previous investigations of first-generation (G1) homoleptic coordination complexes, on which synthetic approaches were developed and spectral and magnetic properties were studied [12]. The goal of this work is to further increase the π-conjugated system by increasing the degree of branching (second-generation, G2) of the complex and introducing additional carbazole fragments.…”

“…The iron(III) complexes, Figure 2, were synthesized by the following procedure [12] − counter-ions. The complexes show a good solubility in solvents such as dichloromethane, chloroform, tetrahydrofuran (THF), toluene, and benzene but they are insoluble in ethanol, water, and hexane.…”

“…The iron(III) complexes, Figure 2, were synthesized by the following procedure [12]. The compounds 4-[3,5-di-(3,6-bis-tert-butylcarbazol-9-yl-benzoyloxy)benzoyloxy]-2-hydroxybenzaldehyde (0.49 mmol), Di(CrB)aldehyde, dissolved in C6H6 (10 mL) at heating, and 3,5-di-[3,6-bis-tert-butylcarbazol-9-yl-benzoyloxy]benzoyloxy-N'-ethyl-N-ethyleneamine (0.49 mmol), Di(CrB)amine, dissolved in EtOH (10 mL) were added to a flask under stirring.…”

“…S2). It was established that the nature of the counter-ion and the number of generations [12] had virtually no effect on τ F . The fluorescence lifetime (τF) of the complexes in CH2Cl2 was determined.…”