Molecular dynamics of a grid-mounted molecular dipolar rotor in a rotating electric field

classical molecular dynamics is applied to the rotation of a dipolar molecular rotor mounted on a square grid and driven by rotating electric field E(v) at T similar or equal to 150 K. The rotor is a complex of Re with two substituted o-phenanthrolines, one positively and one negatively charged, attached to an axial position of Rh-2(4)+ in a [2]staffanedi-carboxylate grid through 2-(3-cyanobicyclo[1.1.1]pent-1-yl)malonic dialdehyde. Four regimes are characterized by a, the average lag per turn: (i) synchronous (a < 1/e) at E(v) = /E(v)/ > E-c(v) [E-c(v) is the critical field strength], (ii) asynchronous (1/e < a < 1) at E-c(v) > E(v) > E-bo(v) > kT/mu, [Ebo(v) is the break-off field strength], (iii) random driven (a similar or equal to 1)at E-bo(v) > E(v) > kT/mu, and (iv) random thermal (a similar or equal to 1)at kT/mu > E(v). A fifth regime, (v) strongly hindered, W > kT, E mu, (W is the rotational barrier), has not been examined. We find E-bo(v)/kVcm(-1) similar or equal to (kT/mu)/kVcm(-1) + 0.13(v/GHz)(1.9) and E-c(v)/kVcm(-1) similar or equal to (2.3kT/mu)/kVcm(-1) + 0.87(v/GHz)(1.6). For v > 40 GHz, the rotor behaves as a macroscopic body with a friction constant proportional to frequency, eta /eVps similar or equal to 1.14 v/THz, and for v < 20 GHz, it exhibits a uniquely molecular behavior.