Characterization of Metal Ions in Coordinating Solvent Mixtures by Means of Raman Spectroscopy

Abstract

Neat DMF and DMA show the in-plane bending δ(O=C-N) vibration at 660 cm -1 and the symmetric stretching ν(N-CH3) vibration at 740 cm -1 , respectively. The metal(II) perchlorate solution usually shows a shoulder band at a higher frequency region of the free solvent band, which is ascribed to the bound Titration Raman spectroscopy has been developed for studying the solvation structure of metal ions in solution. The method affords us the solvation number, and the value thus obtained in neat solvents is in good agreement with that determined by EXAFS. The method is then applied to solvent mixtures, and the individual solvation number for each solvent is extracted. In a solvent mixture of N,N-dimethylformamide (DMF) and N,N,N′,N′-tetramethylurea (TMU), the metal ion prefers DMF to TMU, which is ascribed to the solvation steric effect. The same applies also for the solvent mixture of N,N-dimethylpropionamide (DMPA) and DMF. However, unlike TMU, DMPA changes its conformation from the planar cis to non-planar staggered upon solvation to the metal ion. The enthalpy for the conformational change of DMPA is positive in the bulk, while it is significantly negative in the coordination sphere of the manganese(II) ion. Here, we briefly describe the procedure of measurements and analyses for the titration Raman spectroscopy, and review the solvation structure of the alkaline earth, first transition metal(II) and lanthanide(III) ions in some solvent mixtures in view of solvation steric effect.

Optochemically Responsive 2D Nanosheets of a 3D Metal–Organic Framework Material

“…Neat ZnQ complex thus confers extra degrees of freedom to the coordinated bis‐8‐hydroxyquinoline (8HQ) aromatic moieties around the Zn 2+ center of the guest emitter; this effect is illustrated in the inset of Figure e. In contrast, because Zn metal centers strongly prefer DMF over DMA, coordinated DMF helps to stabilize the ZnQ structure. This is in agreement with the absorption data of ZnQ DMF @OX‐1 nanosheets, where λ max was pinpointed at 387 nm indicating that the ZnQ has coordinated DMF.…”

Solution Properties of Inorganic Contamination in Mixed Solvents: Theory, Progress, and Limitations

“…Complexation of ions is usually more suppressed in a solvent with a high electron-pair donating ability (Burger, 1983;Gutman, 1978). However, this does not apply to solvents with a bulky functional group in the vicinity of the coordinating atom (e.g., in a mixture of DMF + TMU, lanthanide (III) ion preferentially bind to DMF), and complexation is usually enhanced as a result of the solvation steric effects that originate from steric repulsion between solvent molecules simultaneously binding to the ion (Ishiguro et al, 2004;Umebayashi et al, 2005).…”

“…Structural parameters such as ion-ligand atom distances are required in modeling contaminant behavior and transport in mixed-solvent-soil systems. Individual and total solvation numbers can give valuable information on the solvation steric effects on the preferential solvation of ions in solvent mixtures (Ishiguro et al, 2004).…”

“…Structural solvation parameters in mixed solvents have been experimentally determined in a few systems. Ishiguro and coworkers (Ishiguro et al, 2004;Ozutsumi et al, 1997;Ozutsumi and Ohtaki, 1999; Downloaded by [Northeastern University] at 07:36 27 November 2014 Umebayashi et al, 2001aUmebayashi et al, , 2001bUmebayashi et al, 2002) developed a new titration-Raman spectroscopy method for obtaining individual and total solvation numbers of alkaline earth metals, transition metals, and lanthanide (III) perchlorates in such amide solvents as DMF, DMA, DMPA, TMU, AN, NMF, DMSO, and their mixtures. Other researchers have determined these parameters for chromium in MeOH + H 2 O (Melsa and Baltisberger, 1976) for thiocynate salts (Na, K, and NH 4 ) in DMF + H 2 O (Molinou and Tsierkezos, 2008) and for NaClO 4 in DMF + FA (Wagner et al, 2005).…”

Solvation Number and Conformation of N, N-Dimethylacrylamide and N, N-Dimethylpropionamide in the Coordination Sphere of the Cobalt(II) Ion in Solution Studied by FT-IR and FT-Raman Spectroscopy

“…We have so far reported the solvation and complexation of metal(II) ions in some aprotic amide solvents, as well as in their mixtures, in view of the solvation steric effect. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Persson and co-workers reported the solvation thermodynamics of some monovalent ions in N,N-dimethylpropyleneurea (DMPU) 21 and the solvation structure and harogeno complexation of the nickel(II) ion in DMPU 22 and in the crystalline state. 23 Funahashi and Inada et al reported that the solvation number of the Co 2+ ion is 4 in 1,1,3,3-tetramethylurea and its nitromethane mixtures.…”