Ionicity and paramagnetism of strong organic chargehyphen;transfer complexes

摘要

Ionic chargehyphen;transfer (CT) complexes were prepared by mixing neutral solutions of the potent electron acceptor TCNQF4(7,7,8,8hyphen;tetracyanohyphen;2,3,5,6hyphen;tetrafluoroquinodimethane) with the strong donors M2P(5,10hyphen;dihydrohyphen;5,10hyphen;diemethylphenazine) and TMPD(N,N,Nprime;,Nprime;hyphen;tetramethylhyphen;phyphen;phenylenediamine). M2Pndash;TCNQF4lsqb;complex (1)rsqb; and TMPDndash;TCNQF4lsqb;complex (2)rsqb; were obtained as deep blue solids, the latter only in polycrystalline form. Complex (1) crystallizes in the triclinic space groupP1macr; witha= 7.002 (2),b= 8.787(2),c= 9.551(3), agr; = 108.53(2), bgr; = 99.68(2), ggr; = 91.88(2), andZ= 1. The planar M2P+sdot; and TCNQFminus;4sdot; radical ions form mixed regular stacks. The structure refinement gaveR= 0.039 andRw= 0.033 for 1044 counter data. The ionicity ggr; and structure of mixed sdot;sdot;sdot;D+ggr;Aminus;ggr;D+ggr;Aminus;ggr;sdot;sdot;sdot; stacks are closely related to the paramagnetic susceptibility khgr;(T). The two TCNQF4complexes are shown to be the first highly ionic (ggr;gsim;0.9) systems. khgr;(T) for complex (1) follows a Heisenberg antiferromagnetic chain withJ= 175 cmminus;1forTgsim;122 K, below which khgr;(T) decreases steeply as expected for a dimerization transition. khgr;(T) for complex (2) can be fit to a power lawTminus;agr;, with agr; = 0.75plusmn;0.10, and also indicates ggr;gsim;0.9. Both complexes (1) and (2) are on the paramagnetic side of the paramagneticndash;diamagnetic interface, while the finite activation energy for paramagnetism in the less ionic M2Pndash;TCNQ and TMPDndash;TCNQ complexes puts them on the diamagnetic side. The elementary excitations of these related CT complexes with different ionicities are modeled.