Related Experiment Video
Updated: Jul 10, 2026
07:24
Paramagnetic Relaxation Enhancement for Detecting and Characterizing Self-Associations of Intrinsically Disordered Proteins
Published on: September 23, 2021
Studies on TMPD:TCNB; a donor-acceptor with room temperature paramagnetism and n-pi interaction
Prasanna S Ghalsasi1, Brant Cage, J L Yarger
1Department of Chemistry, University of Wyoming, Laramie, Wyoming 82071, USA. prasanna@uwyo.edu
Molecules (Basel, Switzerland)
|November 17, 2007
Summary
Researchers synthesized a N,N,N
Area of Science:
- Crystal Engineering
- Materials Science
- Organic Chemistry
Background:
- Donor-acceptor compounds are crucial in materials science for their unique electronic properties.
- N,N,N',N'-tetramethyl-p-phenylene-diamine (TMPD) is a well-known electron donor.
- 1,2,4,5-tetracyanobenzene (TCNB) is a strong electron acceptor.
Purpose of the Study:
- To synthesize and characterize a novel donor-acceptor compound formed between TMPD and TCNB.
- To determine the crystal structure of the TMPD:TCNB 1:1 complex.
- To investigate the intermolecular interactions within the crystal lattice.
Main Methods:
- Single crystal X-ray diffraction at room temperature.
- Synthesis of the TMPD:TCNB 1:1 complex.
- Crystallographic analysis to determine space group and cell dimensions.
Main Results:
- A black 1:1 donor-acceptor compound of TMPD and TCNB was successfully synthesized.
- The crystal structure was determined, revealing triclinic space group P-1.
- Molecules are arranged in alternate stacks along the a-axis, featuring n-pi interactions instead of typical pi-pi interactions.
Conclusions:
- The synthesized TMPD:TCNB complex exhibits an unusual n-pi interaction between donor nitrogen atoms and acceptor cyano groups.
- This finding provides insights into the structural and electronic properties of organic charge-transfer complexes.
- The crystal packing and intermolecular interactions influence the compound's characteristics.
Related Concept Videos
01:30Paramagnetism
Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
01:14π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds
In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as annulenes. In...
03:02Colors and Magnetism
Color in Coordination Complexes
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 eye.
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 eye.
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
01:15Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT) is an advanced Nuclear Magnetic Resonance (NMR) technique specifically designed to detect and enhance the signals of low-abundance nuclei, such as carbon-13 and nitrogen-15, in small molecules. The fundamental principle behind INEPT is the transfer of polarization from a more abundant and highly polarizable nucleus, typically hydrogen-1, to the low-abundance nucleus of interest. This process effectively boosts the NMR signal of the...
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.