5,5 -Bipyrimidine

The interplay between magnetic coupling and ST in 2,2 -bipyrimidine (bpym)-bridged iron(ll) dinuclear compounds has been studied by magnetic susceptibility and Fe Mossbauer spectroscopy [24]. The molecular stmctures of [Fe(bpym) (NCS)2]2(bpym) and [[Fe(bt)(NCS)2]2(bpym) (bt = 2,2 -bithiazoline) are shown in Fig. 8.12. The magnetic behavior in the form of XmT versus Tplots, being the... 

The study of exchange interactions between transition-metal ions and copper(II) in particular has been an active field of research (Section 6.6.3.6).254-256 In this context, Verdaguer and co-workers investigated complexes (292) and (293), supported by flexible 2,2 -bipyrimidine.257... 

Photophysical studies have been performed on dendrimers 41 [49], built around a [Ru(bpm)3]2+ core (bpm=2,2 -bipyrimidine),and42 [59],built around a [Ru(QP)3]2+ core (QP = 2,2 3, 2" 6",2" -quaterpyridine). In both compounds energy transfer from the peripheral Re(I)-based chromophores to the central Ru(II)-based unit occurs with unitary efficiency. 

Fig. 5 Cyclic and differential voltammograms of RU3O cluster monomer 36 and dimer 37 with orf/zometallated 2,2/-bipyrimidine, recorded in 0.1 M dichloromethane solution of (Bu4N)(PF6). The scan rate is lOOmVs-1 for CV and 20mVs-1 for DPV...

As observed in other oxo-centered triruthenium-acetate complexes, the electronic absorption spectra of 36 and dimer 37 with rt/zr -metal latcd 2,2 -bipyrimidine are... 

One doubly bidentate Lewis base 2,2 -bipyrimidine is coordinated with one germanium atom, while in the case of the analogous lead compound coordination takes place with two lead atoms. 

The [Fe(diimine)2X2] system has been modified by replacing the diimines by unidentate nitrogen donors. [Fe(diimine)(py)2(NCS)2] is a crossover system when the diimine is 2,2 -bipyrimidine or phen [99] but [Fe(py)4(NCS)2] is purely high spin [100]. However, [Fe(py)4(NCS)2] systems containing substituted pyridine derivatives have been shown to exhibit thermal SCO [101], while 4,4 -bipyridine derivatives are able to bridge Fe(II) centres and form polynuclear structures containing SCO [Fe(py)4(NCS)2] centres [102]. SCO is maintained in certain instances when the diimines are replaced by an N4 quadridentate [103,104]. 

Abstract This review reports on the study of the interplay between magnetic coupling and spin transition in 2,2 -bipyrimidine (bpym)-bridged iron(II) dinuclear compounds. The coexistence of both phenomena has been observed in [Fe(bpym)(NCS)2]2(bpym), [Fe(bpym)(NCSe)2]2(bpym) and [Fe(bt)(NCS)2]2(bpym) (bpym = 2,2 -bipyrimidine, bt = 2,2 -bithiazoline) by the action of external physical perturbations such as heat, pressure or electromagnetic radiation. The competition between magnetic exchange and spin crossover has been studied in [Fe(bpym)(NCS)2]2(bpym) at 0.63 GPa. LIESST experiments carried out on [Fe(bpym)(NCSe)2]2(bpym) and [Fe(bt)(NCS)2]2(bpym) at 4.2 K have shown that it is possible to generate dinuclear molecules with different spin states in this class of compounds. A special feature of the spin crossover process in the dinuclear compounds studied so far is the plateau in the spin transition curve. Up to now, it has not been possible to explore with a microscopic physical method the nature of the species... 

Rate and equilibrium constant data, including substituent and isotope effects, for the reaction of [Pt(bpy)2]2+ with hydroxide, are all consistent with, and interpreted in terms of, reversible addition of the hydroxide to the coordinated 2,2 -bipyridyl (397). Equilibrium constants for addition of hydroxide to a series of platinum(II)-diimine cations [Pt(diimine)2]2+, the diimines being 2,2 -bipyridyl, 2,2 -bipyrazine, 3,3 -bipyridazine, and 2,2 -bipyrimidine, suggest that hydroxide adds at the 6 position of the coordinated ligand (398). Support for this covalent hydration mechanism for hydroxide attack at coordinated diimines comes from crystal structure determinations of binuclear mixed valence copper(I)/copper(II) complexes of 2-hydroxylated 1,10-phenanthroline and 2,2 -bipyridyl (399). 

It is also noteworthy that complexes containing ligands such as TAP, HAT, bpz (2,2 -bipyrazine) or bipym (2,2 -bipyrimidine) (Fig. 2), have free non-chelated nitrogen atoms. It has been shown that all these compounds are all more basic in the excited state than the ground state [75,93,94], so that the excited states are already protonated at pH 5-6 on the non-chelated nitrogen atoms. 

Ligands such as 2,2 -bipyrimidine, bipym (110), or 2,3-bis(2-pyridyl)pyrazine, bppz (111), can act as bridging ligands, giving ternary binuclear anions such as [(NC)4Fe (bipym)Fe (H20)4] and [(NC)4Fe LFe (CN)4] with L = bipym or bppz. These and the corresponding... 

The emission from [Ru(bpz)3] is quenched by carboxylic acids the observed rate constants for the process can be rationalized in terms of the protonation of the non-coordinated N atoms on the bpz ligands. The effects of concentration of carboxylate ion on the absorption and emission intensity of [Ru(bpz)3] have been examined. The absorption spectrum of [Ru(bpz)(bpy)2] " shows a strong dependence on [H+] because of protonation of the free N sites the protonated species exhibits no emission. Phosphorescence is partly quenched by HsO" " even in solutions where [H+] is so low that protonation is not evidenced from the absorption spectrum. The lifetime of the excited state of the nonemissive [Ru(Hbpz)(bpy)2] " is 1.1ns, much shorter than that of [Ru(bpz)(bpy)2] (88 nm). The effects of complex formation between [Ru(bpz)(bpy)2] and Ag on electronic spectroscopic properties have also been studied. Like bpz, coordinated 2,2 -bipyrimidine and 2-(2 -pyridyl)pyrimidine also have the... 

The coupling of two azinyl halides, in the presence of an appropriate electron source, also leads to the formation of diaryl compounds. 2-Iodopyrimidine and its derivatives were converted into the symmetrical 2,2 -bipyrimidines (7.88.) using activated copper. This method was found to give superior results,111 compared to the earlier reported nickel chloride-zinc system.112... 

The aerobic oxidation of methane in water catalyzed by [Pt(Mebipym)Cl2] [PV2Mo1004o]5 (Mebipym = N-methy-2,2 -bipyrimidine) complex supported on Si02 was reported [149]. The conjugation of [PV2Mo1004o]5 to a known Pt2 + -bipyrimidine complex by electrostatic interaction could fadlitate the oxidation of the Pt2 + intermediate to a Pt4 + intermediate by 02, resulting in the catalytic aerobic oxidation of methane to methanol in water and then surprisingly further to acetaldehyde via a carbon-carbon coupling reaction. 

Figure 8-24. The reaction of the ruthenium(ii) complex [Ru(bpym)3]2+ with hydroxide ion results in a degradation of one of the ligands. This might be a consequence of initial attack of the hydroxide ion upon the 2,2 -bipyrimidine, although other possibilities cannot be ruled out.

In Table 1, the diimine ligands were either 2,2/-bipyridine or 1,10-phenanthroline, or one of their derivatives, although 2,2,-bipyrazinc and derivatives of 2,2 -bipyrimidine are also listed. Some monodentate chelating ligands contained one or more pyridine functionality and could bind an... 

Chemical Name Benzenesulfonamide, 4-(l,l-dimethylethyl)-N-(6-(2-hydroxyethoxy)-5-(2-methoxyphenoxy)(2,2 -bipyrimidin)-4-yl)-... 

Methoxyphenoxy)-2-(pyrimidin-2-yl)tetrahydropyrimidine-4,6-dione 4,6-Dichloro-5-(2-methoxyphenoxy)-2,2 -bipyrimidine 4-t-Butyl-N-[6-chloro-5-(2-methoxyphenoxy)-2-(pyrimidin-2-yl)-pyrimidin-4-yl] benzenesulfonamide... 

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