Molecules magnetic systems

This compound can be considered as a precursor of more elaborate bpym-based magnetic systems so that formal substitution of the water molecules by more appropriate peripheral ligands, such as bpym and 2,2 -bithi-azoline (bt) together with NCS" or NCSe" counter-ions, allows us to fine tune the ligand field strength around the iron(II) atom, resulting in a rich variety of magnetic behaviour in the [Fe(L)(NCX)2]2(bpym) series. 

We now introduce the concept of the control parameter X (see Section III. A). In the present scheme the discrete time sequence Xk Q transition probability Wt(C C) now depends explicitly on time through the value of an external time-dependent parameter X. The parameter Xk may indicate any sort of externally controlled variable that determines the state of the system, for instance, the value of the external magnetic field applied on a magnetic system, the value of the mechanical force applied to the ends of a molecule, the position of a piston containing a gas, or the concentrations of ATP and ADP in a molecular reaction coupled to hydrolysis (see Fig. 3). The time variation of the control parameter, X = - Xk)/At, is... 

Second, most of the articles cited and the calculations presented are for collisions of diatomic molecules with atoms. The effects of external fields have been studied only for three molecule-molecule collision systems O2-O2 in a magnetic field, NH-NH in a magnetic field, and OH-OH in an electric field. In each case, the calculations are based on significant simplifications of the interaction potential operator. Most of the NH-NH calculations and the O2-O2 studies assume that the collision dynamics occurs on the maximal spin adiabatic potential energy surface of the two-molecule complex. There is only one study that considers the dynamics of NH-NH collisions in a magnetic field with account of transitions to lower spin surfaces [48]. 

We consider the application of this theorem to the evaluation of the integral in Eq. (23) for an ST03G basis calculation of CH4 and a 7r-only calculation of naphthalene. As indicated earlier, we do not attempt to address the ferromagnetism problem, but we can note that the overlaps in naphthalene much more resemble the magnetism system than do the overlaps in a small compact molecule like CH4. 

We again expand in the space-fixed direction, choosing p = 0 to be the direction of the oscillating magnetic field, and then rotate the orbital angular momentum into the molecule-fixed system, retaining only the q = 0 component ... 

The electric quadrupole interaction is handled in exactly the same way as the magnetic hyperfine interactions, by expanding the scalar product (9.36) first in the space-fixed axis system, and then transforming the electronic part of the interaction into the molecule-fixed system. One obtains the result ... 

All of these terms are written in the space-fixed axis system, with Z being the direction of the applied magnetic field, except for the last (the Zeeman anisotropy term), which is expressed in the molecule-fixed system. It is, of course, necessary to transform from space- to molecule-fixed axes in order to evaluate the matrix elements in a case (a) basis. 

In conclusion, at this point one must admit that no dithiolene complex-based compound exhibits a real interplay of conductivity and magnetism. This finding should not result in some kind of inferiority complex, as in only one single molecule-based system, L-(BETS)2FeCl4 and derived mixed Fe—Ga, or Cl— Br species, has it been unambiguously proven that conduction electrons may interact with localized spins (533). 

A similar role has been suggested for water molecules in systems exhibiting more complex, magnetic behavior. In the case of the nickel (II)... 

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