Molecular mechanics calculations (MM3) on silanes

Conformations of silicon-containing rings

“…The relation between the various conformations will be discussed in detail in Section 3.4. In agreement with earlier reports [11,13,15], all methods predict the chair conformation to be the global minimum, hence it will be treated as the dominant conformation.…”

“…The energy differences between chair and twist were calculated to be in the range of 1.7 and 2.2 kcal mol ±1 and between twist and boat about 0.2±0.3 kcal mol ±1 . In a recent MM3 report these energy differences were calculated to be 1.8 and 0.2 kcal mol ±1 , respectively [11].…”

“…Silacyclohexane 1 may be regarded as the first step on a path leading from cyclohexane through 1,3,5-trisilacyclohexane towards cyclohexasilane. Conformations of 1 have been investigated by means of gas phase electron diffraction [13] and molecular mechanics [11,14,15]. We are interested in the conformational behaviour of silicon-containing rings in general and we present in this paper the results of quantum chemical calculations on the structures and relative energies for the basic conformations of molecule 1 as well as its CES calculated by MM3.…”

Synthesis and Structural Study of [5.5](2,6)Pyridinophanes and -cyclophanes Containing Silylene Units

“…To generate all the plausible conformers, we chose to use a Monte Carlo style conformational search (MC) as implemented in MacroModel. , Indeed, in contrast with dynamics, MC calculations do not provide dynamic information on the system, since particles of the system are simply moved randomly according to statistical rules. Concerning the choice of the force field, MM2* was selected because it led to very good parameters for all molecules, in contrast to MM3*, which led to 76−120 “bad” or “general” parameters, mainly due to the O−Si−O and pyridine moieties . The number of conformers found using an energetic window of 15 kJ mol -1 is reported in Table .…”

Anharmonic Molecular Mechanics: Ab Initio Based Morse Parametrizations for the Popular MM3 Force Field

“…First a test set of molecules was created and MM3 atoms types were assigned to each species. This test set primarily included molecules that were used to parametrize the existing MM3 parameters as described in various publications; − however, it was necessary to add a substantial number of additional molecules in order to cover a larger selection of the MM3 bonding types. This test set is listed in the online Supporting Information.…”