Please use this identifier to cite or link to this item:
https://hdl.handle.net/10316/27475
Title: | Intermolecularly-induced conformational disorder in ferrocene, 1-bromoferrocene and 1,1′-dibromoferrocene | Authors: | Silva, Patrícia A. Maria, Teresa M. R. Nunes, Cláudio M. Eusébio, Maria Ermelinda S. Fausto, Rui |
Keywords: | Ferrocene; 1-Bromoferrocene; 1,1′-Dibromoferrocene; Conformational disorder; Polymorphism | Issue Date: | Dec-2014 | Publisher: | Elsevier | Citation: | SILVA, Patrícia A. [et. al] - Intermolecularly-induced conformational disorder in ferrocene, 1-bromoferrocene and 1,1′-dibromoferrocene. "Journal of Molecular Structure". ISSN 0022-2860. Vol. 1078 (2014) p. 90-105 | Serial title, monograph or event: | Journal of Molecular Structure | Volume: | 1078 | Abstract: | Conformational preferences for isolated molecules of ferrocene, 1-bromoferrocene and 1,1′-dibromoferrocene were obtained by combined use of matrix-isolation infrared spectroscopy and quantum chemical calculations. Monomeric ferrocene and 1-dibromoferrocene were found to exist in a low temperature argon matrix (T = 15 K) exclusively in the eclipsed configuration, which corresponds to their most stable conformation in gas phase. On the other hand, for the neat compounds in crystalline phase, intermolecular interactions induce conformational disorder, leading to presence in the room temperature polymorphic forms of monomeric units with the staggered (or nearly staggered) conformation. 1,1′-Dibromoferrocene exists in both gas phase and low temperature argon matrix in two conformers of C2 symmetry (C2-I and C2-II), with eclipsed cyclopentadienyl moieties and Br atoms opposed to H atoms. The populations of the two conformers trapped in the as-deposited matrix were found to correspond to those estimated from theory for the room temperature equilibrium gas phase. By increasing the temperature of the matrix (up to 35 K), the gas phase lower energy form (C2-I) converted to the C2-II form. Besides allowing the precise structural and spectroscopic characterization of the two forms, these studies also revealed that the C2-II conformer (having a largest dipole moment) is stabilized in the matrix media, thus becoming more stable than the C2-I form under these conditions. Very interestingly, the room temperature stable polymorph of the compound (Tfus = 325.4 ± 0.1 K) is composed by 1,1′-dibromoferrocene units exhibiting the C2v symmetry eclipsed conformation with opposed bromine atoms, which for the isolated molecule corresponds to the highest energy conformation along the ring torsional coordinate and is the transition state structure between the two symmetry equivalent C2-II minima. Differential scanning calorimetry, polarized light thermomicroscopy and infrared measurements on 1,1′-dibromoferrocene allowed to identify a new polymorph of the compound, with Tfus = 320.2 ± 0.1 K. On the whole, the results presented in this article represent illuminating examples of intermolecularly-induced conformational disorder in solid phase and of its relevance to polymorphism. | URI: | https://hdl.handle.net/10316/27475 | ISSN: | 0022-2860 | DOI: | 10.1016/j.molstruc.2013.12.031 | Rights: | openAccess |
Appears in Collections: | FCTUC Química - Artigos em Revistas Internacionais |
Files in This Item:
File | Description | Size | Format | |
---|---|---|---|---|
Intermolecularly-Induced Conformational Disorder in Ferrocene.pdf | 2.1 MB | Adobe PDF | View/Open |
SCOPUSTM
Citations
5
checked on Oct 14, 2024
WEB OF SCIENCETM
Citations
10
5
checked on Oct 2, 2024
Page view(s) 50
524
checked on Oct 8, 2024
Download(s) 50
549
checked on Oct 8, 2024
Google ScholarTM
Check
Altmetric
Altmetric
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.