Photon Factory Activity Report 2014 #32 (2015) B

AR-NW2A/2014G048

Controlled Self-Assembly of Donor-Acceptor Molecules Directed by Metal-Metal
Interactions
Kentaro TASHIRONational Institute for Materials Science, Tsukuba 305-0044, Japan
1 Introduction
Construction of p/n molecular heterojunctions via selfassembly is a challenging issue, as it requires asophisticated molecular design strategy to overcome
attractive forces operative between donors and acceptors.
Recently we found that the self-assembly of one
enantiomer of a chiral donor–acceptor dyad successfully
affords ambipolar nanofibers with large charge-carrier
mobilities [1]. As a more universal approach, we
proposed to make use of metal–metal interactions tocontrol the self-assembly of donor–acceptor dyads, byexpecting that the intrinsically homoselective nature ofthese interactions can induce segregation of donor andacceptor. As the first trial, we newly designed dyad 1(Figure1a)composedofcyclometalatedorganoplatinum(II) complex and fullerene, and its selfassembled structure was studied by means of X-ray
crystallography [2].
2 Experiment
A covalently linked dyad of NCN pincer-type
cyclometalated organoplatinum(II) complex and fullerene(1) was newly synthesized by NaOH mediated couplingof the corresponding organoplatinum(II) complex having
a coordinated Cl anion with a fullerene bearing an alkyne
unit, and unambiguously characterized by 1H NMR, IR,and MALDI-TOF-MS analyses. 2 (Figure 1b) wasprepared as reprted.
Slow diffusion of hexane into a CS2 solution of 1 or atoluene solution of 2 afforded red or yellow single
crystals, respectively, suitable for X-ray crystallography.
Single-crystal X-ray diffraction data were collected using
Rigaku Mercury CCD system and processed with
Molecular Structure Corporation model Crystal Clearsoftware at beamline NW-2A of the Photon FactoryAdvanced Ring (KEK, Japan). The diffraction images
were processed by using HKL2000.
Absorption
correction was performed with the program PLATON.
Each structure was solved by the direct methods using
SHELXS-97 and refined by the full-matrix least-squares
method on F2 using SHLEXL-97.
3 Results and Discussion
The ORTEP diagram of 1 proves that its
organoplatinum(II) complex moiety has quite similar
Pt(II)–C(sp), C(sp)–C(sp), and C(sp)–C(sp3) bond lengths
with those of reference organoplatinum(II) complex 2
having no fullerene moiety [2, 3]. In accordance withthese observations, the absorption spectrum of 1a or 1b intheir good solvents such as CH2Cl2, is basically composedof the summation of the absorptions of the corresponding

two starting materials, showing the absence of detectable
intramolecular ground state electronic interaction between
organoplatinum(II) complex and fullerene moieties.

Fig. 1: Molecular structures and ORTEP diagrams of (a)1 and (b) 2. Hydrogen atoms are omitted for clarity.

Fig. 2: ORTEP drawing (50% thermal ellipsoids) of themolecular packing of 1 in its single crystal. C-axis islocated to be perpendicular to the presented cross section.
Carbon atoms of its organoplatinum(II) complex andfullerene moieties are colored in blue and orange,
respectively, while those of disordered hexane molecules
are in grey. Hydrogen atoms are omitted for clarity.
X-ray crystallography on a single crystal of 1 revealed
that the organoplatinum(II) complex and fullerenemoieties of 1 are segregated to afford their alternating
multilayers (Figure 2). Due to the presence of hexane
molecules in the layers of fullerenes, however, their intralayer contacts are partly disturbed. Moreover, only one ofthe pyridyl rings of the pincer ligand exhibits a sign of thestacking interaction with neighboring organoplatinum(II)Photon Factory Activity Report 2014 #32 (2015) B

complex moieties, suggesting that the packing structureof 1 would not be suitable for the evaluation of chargetransporting capability. In fact, no FET response wasobserved on the powder sample of crystalline 1.
References[1] K. Tashiro et al., J. Am. Chem. Soc., 132, 6628–6629(2010).
[2] CCDC entry 1041759.
[3] CCDC entry 1048124.
* TASHIRO.Kentaro@nims.go.jp