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Evidences for a localized chromophore in the Ti(IV)/squarate complex: a resonance Raman investigation
1Laboratório de Espectroscopia Molecular, Instituto de Química da Universidade de São Paulo, SP, Brazil.
Summary
This study reveals strong interactions between titanium(IV) and oxocarbon anions like squarate and croconate. Enhanced Raman spectroscopy indicates a ligand-to-metal charge transfer state localized in the titanium-carbon-oxygen bonds.
Area of Science:
- Coordination Chemistry
- Spectroscopy
- Materials Science
Background:
- Previous studies explored interactions between oxocarbon anions and metal ions.
- Understanding metal-ligand interactions is crucial for materials science and catalysis.
Purpose of the Study:
- To investigate the interaction between titanium(IV) and squarate/croconate anions.
- To elucidate the nature of the resulting complexes using spectroscopic methods.
Main Methods:
- Preparation of titanium(IV) acidic solutions with squarate or croconate.
- UV-Vis absorption spectroscopy to observe spectral changes.
- Resonance Raman spectroscopy to analyze vibrational modes.
Main Results:
- Formation of colored solutions upon mixing titanium(IV) with oxocarbon anions.
- Significant enhancement of specific oxocarbon vibrational modes, particularly the nu(C=O) mode.
- Observation of a ligand-to-metal charge transfer (LMCT) state.
Conclusions:
- A strong interaction exists between Ti(IV) and oxocarbon anions via the CO moieties.
- The LMCT state is localized within the Ti(IV)-CO bonds.
- The enhancement mechanism is likely Albrecht's A term (Franck-Condon mechanism).