REDOX RESPONSIVE BI TRI-NUCLEAR COMPLEXES INCORPORATING FERROCENYL UNIT - SYNTHESIS, CHARACTERIZATION, PHYSICOCHEMICAL STUDIES AND X-RAY STRUCTURE OF [C5H5FEC5H4CH=CHC5H4N-CH3]PF6 WITH A MIRROR CREATING DISORDER/

(Trans-1-(4-pyridyl)-ethylene) ferrocene, L reacts with K[Ru-III(edtaH )]Cl to form binuclear complex. K[Ru(III()edtaH)]Cl exist as Ru-III(ed taH)(H2O) in aqueous solution and substitution of the aqua molecule by L occurs within the stopped flow time scale. Rate constants for the r eaction are 1620 +/- 20, 2080 +/- 35, 2690 +/- 50 M-1 s(-1) at 28, 34 and 39.9 degrees C, respectively [Delta H# is 30.3 +/- 1.1 kJ mol(-1) and Delta S# is -124 +/- 4 J K-1 mol(-1)]. R-II(2,2'-bipy)(2)Cl-2 reac ts with L to form bi/trinuclear complexes, [Ru-II(2,2'-bipy)(2)LCl]PF6 and [Ru-II(2,2'-bipy)(2)L-2](PF6)(2), depending on the reaction condi tions. Luminescence of the Ru-II(2,2'-bipy)(2)(py)(2)(2+) center in th e trinuclear complexes is completely quenched presumably through energ y transfer pathway. There exist a moderate to weak electrochemical int eraction between the two redox centers either in N-methylated form of L or in the bi/trinuclear complexes derived from Ru(II) or Ru(III). Al l these new bi/trinuclear complexes are characterized by physicochemic al methods. Single crystal X-ray structure of [L-CH3]PF6 is reported. A very low value of powder SHG efficiency observed earlier for this sa lt can now be well understood in terms of the centrosymmetric molecula r arrangement created due to the disorder in the crystal. (C) 1997 Els evier Science S.A.