The van der Waals radius of mercury

Fourier-transform infrared (FT-IR), Raman (RS), and surface-enhanced Raman scattering (SERS) spectra of β-hydroxy-β-methylobutanoic acid (HMB), L-carnitine, and N-methylglycocyamine (creatine) have been measured. The SERS spectra have been taken from species adsorbed on a colloidal silver surface. The respective FT-IR and RS band assignments (solid-state samples) based on the literature data have been proposed. The strongest absorptions in the FT-IR spectrum of creatine are observed at 1398, 1615, and 1699 cm−1, which are due to νs(COOH) + ν(CN) + δ(CN), ρs(NH2), and ν(CO) modes, respectively, whereas those of L-carnitine (at 1396/1586 cm−1 and 1480 cm−1) and HMB (at 1405/1555/1585 cm−1 and 1437–1473 cm−1) are associated with carboxyl and methyl/methylene group vibrations, respectively. On the other hand, the strongest bands in the RS spectrum of HMB observed at 748/1442/1462 cm−1 and 1408 cm−1 are due to methyl/methylene deformations and carboxyl group vibrations, respectively. The strongest Raman band of creatine at 831 cm−1 (ρw(RNH2)) is accompanied by two weaker bands at 1054 and 1397 cm−1 due to ν(CN) + ν(RNH2) and νs(COOH) + ν(CN) + δ(CN) modes, respectively. In the case of L-carnitine, its RS spectrum is dominated by bands at 772 and 1461 cm−1 assigned to ρr(CH2) and δ(CH3), respectively.



The analysis of the SERS spectra shows that HMB interacts with the silver surface mainly through the COO−, hydroxyl, and CH2 groups, whereas L-carnitine binds to the surface via COO− and N+(CH3)3 which is rarely enhanced at pH = 8.3. On the other hand, it seems that creatine binds weakly to the silver surface mainly by NH2, and CO from the COO− group. Copyright © 2006 John Wiley & Sons, Ltd.

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Food additives characterization by infrared, Raman, and surface‐enhanced Raman spectroscopies

Dimethylcyanamide (N identical withCNMe(2)) has been coordinated to both hard and soft electrophiles ((NH(3))(5)Co(3+), (NH(3))(5)Os(3+), (dien)Pt(2+)) which activate ( approximately x10(6)) the nitrile toward attack by nucleophiles such as ammonia and hydroxide. Amination with liquid ammonia gave a rare coordinated guanidine (N,N-dimethylguanidine) ligand, which NMR spectra and X-ray crystal structures show to be charge neutral rather than anionic. Crystals of [(NH(3))(5)CoNH=C(NH(2))NMe(2)](S(2)O(6))(3/2).H(2)O, CoC(3)H(26)N(8)O(10)S(3), were triclinic, space group Po, a = 11.565(2) A, b = 10.629(5) A, c = 8.026(1) A, alpha = 84.93(3) degrees, beta = 76.01(1) degrees, gamma = 73.82(3) degrees, V = 919.2(5) A(3), Z = 2, and R(F)() (R(w)(F)()) = 0.038 (0.047) for 3262 observed reflections (I > 3.0 sigma(I)). Crystals of [(dien)PtNH=C(NH(2))NMe(2)](CF(3)SO(3))(2), PtC(9)H(22)N(6)O(6) S(2)F(6), are monoclinic, space group P2(1)/c, a = 13.857(4), b = 14.748(4) A, c = 22.092(4) A, beta = 105.38(2) degrees, V = 4353(2) A(3), Z = 8, and R(F)() (R(w)(F)()) = 0.034 (0.038) for 6778 reflections. Coordination geometries around the metals are octahedral and square planar, respectively, the guanidine skeletons being planar with bond angles and lengths characteristic of the metal-imino (rather than metal-amino) tautomer. The complexes are very stable in coordinating solvents (DMSO; water, pH 3-11) indicating high affinity of guanidine ligands for metal ions. Hydration of the dimethylcyanamide ligand is base-catalyzed, and first-order in [OH(-)] (0.05-0.5 M NaOH; k = k(s) + k(OH)[OH(-)], k(OH) = 2-5 M(-)(1) s(-)(1), 25 degrees C), in each case producing coordinated N,N-dimethylurea ([dienPtNHCONMe(2)](+), [(NH(3))(5)CoNHCONMe(2)](2+), [(NH(3))(5)OsNHCONMe(2)](2+)). Hydration rates are surprizingly similar despite differing radial extensions of the metal d-orbitals, a finding consistent with their comparable polarizing powers but contrary to expectation from other work. The relevance of metal activation of nitriles to biological systems is discussed.

Models for Arginine-Metal Binding. Synthesis of Guanidine and Urea Ligands through Amination and Hydration of a Cyanamide Ligand Bound to Platinum(II), Osmium(III), and Cobalt(III).

Mercury organometallic compounds. Classification and analysis of crystallographic and structural data

Reactivity of copper(II) peptide complexes with bioligands (benzimidazole and creatinine)

Phenylmercury(II) replaces a proton of creatine, H2NC+(NH2)NMeCH2C02-, in basic solution to form the zwitterionic
complex PhHgNHC+(NH2)NMeCH2CO2-. Creatine and creatinine (C4H7N30) react with PhHg((OH)N03)I/2 in aqueous ethanol to form a 2:l complex [(PhHg)2(C4H6N30][N03] which exists in two crystalline forms. Creatinine forms a 1:l
complex [PhHg(C4H7N30)][N03].1/2H20 at pH 1.4 on reaction with PhHg((OH)N03)l/2 in the presence of nitric acid.
The 1:l and 2:l complexes may be interconverted. Creatinine hydronitrate, [H2NCNMeCH2CONH][NO3], and the PhHg(II) complexes of creatinine have similar infrared (including deuterated derivatives) and 1H NMR spectra, consistent with retention of the creatinine ring and presence of a guanidinium group in the complexes. An X-ray structural analysis of one crystalline form of the 2:l complex shows bonding of PhHg(II) groups to the exocyclic and ring nitrogens of creatinine to form the cation
[PhHgNHCNMeCH2CONHgPh]+.

M. Fyfe

Papers

Organometallic compounds containing a guanidinium group. Phenylmercury(II) derivatives of creatine and creatinine

Complexes of phenylmercury(II) with dicyandiamide