Synthesis, structure, and excited state kinetics of heteroleptic Cu(i) complexes with a new sterically demanding phenanthroline ligand

In this report we describe the synthesis of a new phenanthroline ligand, 2,9-di(2,4,6-tri-isopropyl-phenyl)-1,10-phenanthroline (bL2) and its use as the blocking ligand in the preparation of two new heteroleptic Cu(i)diimine complexes. Analysis of the CuHETPHEN single crystal structures shows a distinct distortion from an ideal tetrahedral geometry around the Cu(i) center, forced by the secondary phenanthroline ligand rotating to accommodate the isopropyl groups of bL2. The increased steric bulk of bL2 as compared to the more commonly used 2,9-dimesityl-1,10-phenanthroline blocking ligand prohibits intramolecular ligand-ligand interaction, which is unique among CuHETPHEN complexes. The ground state optical and redox properties of CuHETPHEN complexes are responsive to the substitution on the blocking ligand even though the differences in structure are far removed from the Cu(i) center. Transient optical spectroscopy was used to understand the excited state kinetics in both coordinating and non-coordinating solvents following visible excitation. Substitution of the blocking phenanthroline ligand has a significant impact on the ³MLCT decay and can be used to increase the excited state lifetime by 50%. Electronic structure calculations established relationships between ground and excited state properties, and general entatic state concepts are discussed for copper photosensitizers. This work contributes to the growing library of CuHETPHEN complexes and broadens the fundamental understanding of their ground and excited state properties.

Stereoselectivity of formation of monoterpene - Amino acids hybrid molecules in the reaction of monoterpene nitroso chlorides with α-amino acid derivatives

Reaction of nitrosochlorides of natural monoterpene hydrocarbons (+)-3-carene and (-)-α-pinene with L-amino acids and their methyl esters results in stereoselective formation of terpene-amino acids hybrids, which belong to the series of α-substituted amino oximes. The reaction with an excess of racemic DL-amino acids and their derivatives induces partial resolution of the amino acid components and formation of the diastereomeric mixtures of the terpene-amino acids hybrids, with diastereomeric excess varying from 0 to 100%.

Sandwich-shaped silver(i) metallomacrocycles encapsulating a XF62? (X = Si, Ge and Sn) anion

A series of sandwich-shaped complexes based on two square tetranuclear Ag(I) metallomacrocycles, [[Ag4(pprd)4]2(XF6)]-(BF4)6.8MeNO2 (pprd = 4-(2-pyridyl)pyrimidine; X = Si, Ge and Sn), in which a XF6(2-) anion is encapsulated, were prepared and their structures were characterized both in the solid state and solution.

New discrete metallocycles incorporating palladium(ii) and platinum(ii) corners and dipyridyldibenzotetraaza[14]annulene side units

The interaction of the extended, fully-conjugated macrocycle, dipyridyldibenzotetraaza[14]annulene (1), with the square planar palladium(II) and platinum(II) complexes [M(dppp)(triflate)(2)].2H(2)O (M = Pd, Pt) has been investigated in both solution and the solid state. In each case solid products showing a 1:1 ratio of metal complex: 1 were obtained. A 1:1 mixture of and [Pd(dppp)(2)(triflate)(2)].2H(2)O in dichloromethane yielded two major products as evidenced by the presence of two singlets in the (31)P {(1)H}-NMR spectrum of the reaction solution. Similarly, two singlets were evident in the corresponding spectrum obtained on dissolving the 1:1 product in nitrobenzene. The temperature and concentration dependence of the spectra clearly showed that the two species present in each case were in equilibrium. From the temperature dependence, the low field signal was assigned to the smaller of the two species. Broadly parallel behaviour was observed for the corresponding platinum-containing system. The MS-ESI spectrum of the platinum derivative showed the presence of a dinuclear species corresponding to [Pt(dppp)(1)](2)(2+) and an X-ray structure of this product confirmed that a corresponding dinuclear complex exists in the solid state. This product has a geometry in which two curved macrocyclic side units bridge two metal centres to yield an ellipse-shaped structure. Attempts to employ pulsed-field gradient spin-echo (PGSE) (31)P NMR confirmed that the lower-field resonance corresponded to the smaller of the two species in solution. STM (HOPG) imaging of the palladium- and platinum-containing products revealed arrays that appear to be composed of "zipper-like" rows of dimer units, with the dimensions of the latter comparing well with those found in the X-ray structure of [Pt(dppp)(1)](2)(2+).