442873-72-5Relevant academic research and scientific papers
Molecular structure and DFT investigations on new cobalt(II) chloride complex with superbase guanidine type ligand
Soliman, Saied M,M Abu-Youssef, Morsy A,Albering, J?rg,El-Faham, Ayman
, p. 2137 - 2149 (2015)
The new [Co(btmgn)Cl 2] complex and the 1,8-bis(tetramethylguanidino)naphthalene (btmgn) ligand were synthesized and characterized. The X-ray single crystal investigation showed distorted tetrahedral geometry around the Co(II) ion. The geometry of the btmgn and [Co(btmgn)Cl 2] complex was optimized using the B3LYP/6-311G(d,p) method. The calculated geometric parameters at the optimized structure of the [Co(btmgn)Cl 2] complex showed good agreement with our reported X-ray structure. The two tetramethylguanidino groups are in a cis-type position to the naphthalene ring plane both in the free and coordinated btmgn. The large red shift of the υ C=N mode upon coordination indicates the strong ligand-metal interactions. The calculated natural charges using natural bond orbital (NBO) analysis at the two coordinated Cl-atoms are not equivalent. Also the two LP(4)Cl →LP?(3)Co intramolecular charge transfer interaction energies (E (2)) are 29.00 and 39.17 kcal/mol, respectively. The two Co-Cl bonds are not equivalent where the longer Co-Cl bond has more electronegative chlorine atom than the shorter one. Molecular electrostatic potential (MEP) study of the btmgn ligand showed that the N4 and N7 atoms are the most reactive nucleophilic centers for the coordination with the Co 2+ ion. The [Co(btmgn)Cl 2] complex has higher polarizability (α 0), first hyperpolarizability (β 0) and lower energy gap (ΔE) than the free ligand. The TD-DFT calculations predicted the transition bands at 337.2 nm (f =0.2299, H →L) and 342.6 nm (f =0.1465, H-2/H →L) for the btmgn and [Co(btmgn)Cl 2], respectively.
1,8-Bis(tetramethylguanidino)naphthalene (TMGN): A new, superbasic and kinetically active "proton sponge"
Raab, Volker,Kipke, Jennifer,Gschwind, Ruth M.,Sundermeyer, Joerg
, p. 1682 - 1693 (2007/10/03)
1,8-Bis(tetramethylguanidino)naphthalene (TMGN, 1) is a new, readily accessible, and stable "proton sponge" with an experimental pKBH+ value of 25.1 in MeCN, which is nearly seven orders of magnitude higher in basicity than the classical proton sponge 1,8-bis(dimethylamino)-naphthalene (DMAN). Because of the sterically less crowded character of the proton-accepting sp2-nitrogen atoms, TMGN also has a higher kinetic basicity than DMAN, which is shown by time-resolved proton self-exchange reactions. TMGN is more resistant to hydrolysis and is a weaker nucleophile towards the alkylating agent EtI in comparison to the commercially available guanidine 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD). Crystal structures of the free base, of the mono- and bisprotonated base were determined. The dynamic behavior of all three species in solution was investigated by variable-temperature 1H NMR experiments. ΔG≠ values obtained by spectra simulation reveal a concerted mechanism of rotation about the C-N bonds of the protonated forms of TMGN.
