DPP Dyes as Ligands in Transition‐Metal Complexes

• Published in: Chemistry : a European journal Vol. 8; no. 17; pp. 4047 - 4055
• Main Authors: Lorenz, Ingo‐Peter, Limmert, Michael, Mayer, Peter, Piotrowski, Holger, Langhals, Heinz, Poppe, Martin, Polborn, Kurt
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY‐VCH Verlag 02.09.2002
• Subjects: coinage metal complexes; dyes; fluorescence; structure elucidation; UV/Vis spectroscopy
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/1521-3765(20020902)8:17<4047::AID-CHEM4047>3.0.CO;2-M

The DPP dyes (=diketopyrrolopyrrole) 1 are deprotonated to give the corresponding dianions 2. These are treated with two moles of the transition‐metal complexes [LnMX]=[(Ph3P)2MX] (M=Cu, Ag; X=Cl, NO3), [(Ph3P)AuCl], [(Et3P)AuCl], [(tBuNC)AuCl], [(Ph3P)2PdCl2], and [(Ph3P)2PtCl2] to give the novel bismetalated DPP dyes [LnMN{C3R1(O)}2NMLn] (4–10). In comparison with the starting materials, these compounds show better solubilities, high fluorescence quantum yields (Φ≥80 %), and bathochromic absorptions. The compounds 4 c, 5 a, 6 b, 6 c, 6 e, 7 c, and 8 c were characterized by X‐ray crystallography. The copper and silver atoms in 4 c and 5 a are trigonal planar and are surrounded by the P atoms of the phosphane ligands and the N atom of the DPP dianion 2. Both metals are somewhat forced out‐of‐plane, and the P2M plane and the phenyl planes of R1 are twisted by >70° and <25°, respectively, towards the chromophore plane. The gold atoms in 6–8 are linearly coordinated to one N and one P (6 b, c, e, 7 c) or one C atom (8 c), respectively. The gold atoms are only slightly pressed out‐of‐plane, and the P substituents are staggered so that there is enough space for the planarization of R1 into the plane of the chromophore. Compound 8 c shows intermolecular d10–d10 interactions between AuI centers of different molecules, and these interactions lead to infinite chains of parallel orientated molecules in a gauche conformation of neighbors (torsion angle=150°) in the crystal. DPP‐type color pigments were deprotonated and coordinated to the coinage metals copper, silver, and gold as well as palladium and platinum (see structure, LnM=[(Ph3P)2M] (M=Cu, Ag), [(Ph3P)Au], [(Et3P)Au], [(tBuNC)Au], [(Ph3P)ClPd], [(Ph3P)2ClPt]; R1=C6H5, 4‐MeC6H4, 4‐ClC6H4, 4‐NCC6H4, 2‐C5H4N, 2‐C4H3S). DPP dyes have novel properties such as improved solubilities, high fluorescence quantum yields, and bathochromic absorptions. The crystal structures of seven DPP complexes indicate a torsion of the planes of phenyl substituents with respect to the chromophore plane depending on the complex fragment. The effects of the different metals, ligands, and substituents in the chromophore are investigated and discussed.