Speciation in solution, solid state spectroscopy and vapochromism of [Pt(trpy)(NCS)]SbF(6) where trpy =
John S Field1, Craig D Grimmer, Orde Q Munro
1School of Chemistry, University of KwaZulu-Natal, Private Bag X01, Pietermaritzburg, 3201, South Africa. fieldj@ukzn.ac.za
Dalton Transactions (Cambridge, England : 2003)
|January 28, 2010
Summary
This study synthesizes a platinum-terpyridine complex, [Pt(trpy)(NCS)]SbF(6), which exhibits temperature-dependent emission and selective vapochromic behavior. The complex
Area of Science:
- Coordination Chemistry
- Materials Science
- Spectroscopy
Background:
- Platinum complexes with polypyridyl ligands are of interest due to their photophysical properties.
- The thiocyanate (SCN-) ligand can coordinate to metal centers through either nitrogen or sulfur, leading to linkage isomerism.
- Metallophilic interactions in platinum complexes can influence solid-state properties.
Purpose of the Study:
- To synthesize and characterize a new platinum-terpyridine complex containing a thiocyanate ligand.
- To investigate the structural, spectroscopic, and photophysical properties of the synthesized complex.
- To explore the vapochromic behavior and its relationship with solid-state structure and metallophilic interactions.
Main Methods:
- Metathesis reaction to synthesize the platinum complex.
- Single crystal X-ray diffraction for structural determination.
- (15)N NMR spectroscopy to study linkage isomerism.
- UV-Vis absorption and emission spectroscopy to analyze photophysical properties.
- Vapochromism studies using various solvent vapors.
Main Results:
- Yellow crystals of [Pt(trpy)(NCS)]SbF(6)·CH(3)CN were obtained, with N-bound thiocyanate and Pt(2) dimers (Pt-Pt separation 3.293(1) Å).
- The complex exists as a mixture of N- and S-bound isomers in solution, with the N-bound isomer being dominant.
- The complex exhibits temperature-dependent emission and selective, reversible vapochromic behavior, changing color from maroon to yellow upon exposure to acetonitrile, DMF, or pyridine vapors.
- Vapochromism is attributed to the disruption and formation of Pt-Pt metallophilic interactions.
Conclusions:
- A novel platinum-terpyridine complex with tunable solid-state properties has been synthesized.
- The complex displays interesting photophysical and vapochromic behaviors driven by structural changes and metallophilic interactions.
- This study highlights the potential of such complexes in sensing applications and materials science.
Related Concept Videos
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
NMR Spectroscopy of Benzene Derivatives
Simple unsubstituted benzene has six aromatic protons, all chemically equivalent. Therefore, benzene exhibits only a singlet peak at δ 7.3 ppm in the 1H NMR spectrum. The observed shift is far downfield because the aromatic ring current strongly deshields the protons. Any substitution on the benzene ring makes the aromatic protons nonequivalent, and the protons split each other. The peak is, therefore, no longer a singlet and the splitting pattern and their associated coupling constants depend...
IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...
Aromatic Hydrocarbon Cations: Structural Overview
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group with both...
Removing one hydrogen from the intervening CH2 group with both...
UV–Vis Spectroscopy of Conjugated Systems
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in the...
One of the factors influencing λmax is the extent of conjugation in the...


