β–α Photoisomerization of Cobaloxime Complexes in the Solid State. 5. Reaction Rate Reduced by a Hydrogen Bond

Abstract

The crystal structures of three cobaloxime complexes with different axial base ligands have been analyzed by X-ray analysis at room temperature. I: (2-Cyanoethyl)bis(dimethylglyoximato)((S)-phenylalaninol)cobalt(III); the crystal is orthorhombic, the space group being P212121, Z = 4 with a = 9.416(3), b = 27.184(3), c = 9.184(3) Å. II: (2-Cyanoethyl)bis(dimethylglyoximato)((S)-phenyl-alanine methyl ester)cobalt(III); the crystal is monoclinic, the space group being P21, Z = 4 with a = 14.376(2), b = 11.988(2), c = 14.874(1) Å, and β = 101.05(1)°. III: (2-Cyanoethyl)bis(dimethylglyoximato)(methyldiphenylphosphine)cobalt(III); the crystal is monoclinic, the space group being P21/n, Z = 4 with a = 11.558(4), b = 15.542(3), c = 14.393(5) Å, and β = 91.02(4)°. The structures were refined by the full-matrix least-squares method to final R values of 0.041, 0.052, and 0.044 for 2340, 3287, and 4400 observed reflections, respectively. The photoisomerization rates of I, II, and III in the solid state were obtained from the changes in the IR spectra. The rate of I was insignificantly small, but the rates of II and III were calculated to be 0.1 × 10−4 and 1.9 × 10−4 s−1, respectively, assuming first-order kinetics. The 2-cyanoethyl groups in the three complex crystals take perpendicular conformations to their cobaloxime planes. The 2-cyanoethyl group of I makes a hydrogen bond with the N–H group of the neighboring molecule. The non-reactivity of I may be brought about by the hydrogen bond.

Dynamic motion and various reaction paths of cobaloxime complexes in crystalline-state photoreaction

“…In order to examine the relation between reaction rate and crystal structure more systematically, 10 cobaloxime complexes with different axial base ligands were prepared. They have pip [100], 3cpy [101], 4-aminopyridine (4apy) [101], 3epy [102], 4epy [102], 3apy [103,104], 1-aminobenzene (1abz), [103,104] S-phenylalaninol (S-pala) [105], S-phenylalanine methyl ester (S-pame) [105] and dpmp [105] as the axial base ligands. The molecular structures of ten crystals are similar to those observed in the two forms of the py complex, as shown in Figure 89.…”

Hydrophobic-exterior layer structures and magnetic properties of trinuclear copper complexes with chiral amino alcoholate ligands

“…[24][25][26][27][28][29][30] Ongoing work on metal complexes with easily accessible amino alcoholate (amino alkoxido) ligands [24][25][26][27][28][29][30] prompted us to utilize chiral amino alcoholate ligands for the formation of homochiral SBUs for extended coordination polymeric structures. Known structures with the enantiopure b-amino alcoholate ligands 31 2-amino-propan-1-olate (ap), [32][33][34] 2-amino-butan-1olate (ab), 34,35 (S)-2-amino-2-phenylethanolate (aPhe), 20,36 2-amino-3-methyl-pentan-1-olate, 33 (1S,2S)-(+)-1-phenyl-2amino-1,3-dihydroxypropanolate, 37 D(À)-1,2-diphenyl-2-oxyethylamine, 38 (S)-phenylalaninolate, 39 2-amino-1-phenyl-propan-1olate (norphedrine), 33,40 are so far restricted to molecular metal complexes. 20,[31][32][33][34][35][36][37][38][39][40] Coordination polymers with alcoholato-O-bridged binuclear copper ethanolamine complexes as SBUs have been reported (Scheme 1).…”

“…Known structures with the enantiopure b-amino alcoholate ligands 31 2-amino-propan-1-olate (ap), [32][33][34] 2-amino-butan-1olate (ab), 34,35 (S)-2-amino-2-phenylethanolate (aPhe), 20,36 2-amino-3-methyl-pentan-1-olate, 33 (1S,2S)-(+)-1-phenyl-2amino-1,3-dihydroxypropanolate, 37 D(À)-1,2-diphenyl-2-oxyethylamine, 38 (S)-phenylalaninolate, 39 2-amino-1-phenyl-propan-1olate (norphedrine), 33,40 are so far restricted to molecular metal complexes. 20,[31][32][33][34][35][36][37][38][39][40] Coordination polymers with alcoholato-O-bridged binuclear copper ethanolamine complexes as SBUs have been reported (Scheme 1). These SBUs are connected with bridging ligands (X), such as 1,2-bis(4-pyridyl)ethylene, 26 pyrazine, 27 p-bis(4-pyridyl)benzene, 9,10-bis(4-pyridyl)anthracene, bis-(4-pyridyl)disulfide, tris (3-pyridyl)benzene, 25 3-hydroxobenzoate, 28 acetate 29 or with pseudo halogenides.…”

Photoisomerization of (2-cyanoethyl)(isonicotinic acid)cobaloxime complex in a series of isostructural host–guest complex crystals

“…As a consequence of these investigations, three factors were found to control the reaction rate: the conformation of the reactive group, 12 the reaction cavity 13 and the hydrogen bond of the reactive group with the neighbouring molecule. [14][15][16] This gave us an idea that the formation of the host-guest complex crystal is a very effective method for changing the crystal packing around the reactive group, namely varying the reaction cavity. Especially, if the hosts can get close to the reactive group, the reactivity will be easily controlled by changing the hosts.…”