Related Experiment Video
Updated: Jul 25, 2025

Preparation of 6-aminocyclohepta-2,4-dien-1-one Derivatives via Tricarbonyltroponeiron
Published on: August 12, 2019
Enabling Valence Delocalization in Iron(III) Macrocyclic Complexes through Ring Unsaturation
Reese A Clendening1, Stephanie S Delancey1, Andrew T Poore1
1Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States.
Abstract:
The complexes [FeIII(HMC)(C2DMA)2]CF3SO3 ([2]OTf) and [FeIII(HMTI)(C2Y)2]CF3SO3 ([3a-c]OTf) have been prepared and thoroughly characterized (HMC = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; HMTI = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene; Y = Fc (ferrocenyl, [3a]OTf), 4-(N,N-dimethyl)anilino (DMA, [3b]OTf), or 4-(N,N-bis(4-methoxyphenyl)anilino (TPA, [3c]OTf); OTf- = CF3SO3-)). Vibrational and electronic absorption spectroelectrochemical analyses following one-electron oxidation of the ethynyl substituent Y revealed evidence of strong coupling in the resultant mixed valent species for all HMTI-based complexes. However, the analogous mixed valent ion based on [2]OTf appeared to be more localized. Thus, the tetra-imino macrocycle HMTI has enabled significant valence delocalization along the -C2-FeIII-C2- bridge. Electron paramagnetic resonance and Mössbauer spectroscopic studies of [3b]OTf reveal that the π-acidity of HMTI lowers the energy of the FeIII dπ orbitals compared to the purely σ-donating HMC. This observation provides a basis for the interpretation of the macrocycle-dependent valence (de)localization.
More Related Videos
09:45Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
Published on: March 20, 2017
07:49Characterizing Lewis Pairs Using Titration Coupled with In Situ Infrared Spectroscopy
Published on: February 20, 2020
Related Concept Videos
Valence Bond Theory
Complexation Equilibria: Factors Influencing Stability of Complexes
Structural Isomerism
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
Complexation Equilibria: The Chelate Effect
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3