Paul Kautny

Structure-Property Relationships in Click-Derived Donor-Triazole-Acceptor Materials.

To shed light on intramolecular charge-transfer phenomena in 1,2,3-triazole-linked materials, a series of 1,2,3-triazole-linked push-pull chromophores were prepared and studied experimentally and computationally. Investigated modifications include variation of donor and/or acceptor strength and linker moiety as well as regioisomers. Photophysical characterization of intramolecular charge-transfer features revealed ambipolar behavior of the triazole linker, depending on the substitution position. Furthermore, non-centrosymmetric materials were subjected to second-harmonic generation measurements, which revealed the high nonlinear optical activity of this class of materials.

Structure–property studies of P-triarylamine-substituted dithieno[3,2-b:2′,3′-d]phospholes

The synthesis of 10 novel P-substituted dithienophosphole oxide compounds applying phenylcarbazole and indolocarbazole donors is presented. Based on photo-physical and theoretical investigations, the study reveals that the pyramidal geometry of the phosphorus allows for the synthesis of charge transfer materials by introducing strong exocyclic donor groups but suppresses intramolecular charge transfer below a certain donor strength threshold, which is an appealing structural feature for the design of donor–acceptor materials. The triplet energies of the phenylcarbazole based compounds are in the range of 2.49–2.65 eV, sufficiently high for potential applications as host materials in PhOLEDs. By contrast, the introduction of indolocarbazole, the weakest employed donor, yields materials exhibiting a significantly higher triplet energy of up to 2.87 eV and a remarkably low singlet–triplet splitting (0.18 eV). In addition an interesting example of an intramolecular electronic through-space interaction has been observed for the ortho-linked phenylcarbazole derivative.

Crystal chemistry of layered structures formed by linear rigid silyl-capped molecules

Silyl capped aryl bis-ene–yne compounds and their derivatives possess a rich crystal chemistry: merotypism, polymorphism, polytypism, twinning and incommensurate modulation.

Thieno[3,4-c]pyrrole-4,6-dione as novel building block for host materials for red PhOLEDs

In the presented work the electron accepting thieno[3,4-c]pyrrole-4,6-dione is introduced as a novel building block for donor–acceptor based host materials for Phosphorescent Organic Light Emitting Diodes (PhOLEDs). A series of three regioisomers consisting of the thieno[3,4-c]pyrrole-4,6-dione acceptor and carbazole donors linked via a phenylene linker was prepared and the impact of the phenylene substitution pattern on the molecular properties was analyzed. Regarding their applicability as host materials, the newly developed materials were investigated in red PhOLED devices achieving a high current efficiency of 30.6 cd A−1 corresponding to an external quantum efficiency of 17.7% and a high power efficiency of 23.8 lm W−1. Thus, we present the first successful application of the thieno[3,4-c]pyrrole-4,6-dione building block in host materials for PhOLEDs.

Functional organic click-materials: application in phosphorescent organic light emitting diodes

In the presented work click chemistry is utilized to introduce 1,2,3-triazoles as a functional linker in organic donor–acceptor materials. A systematic series of materials was prepared and characterized to investigate the effect of the linkage mode on the molecular properties. The 1,2,3-triazole linker allowed control of the degree of intramolecular charge transfer over a wide range depending on the substitution pattern of the triazole moiety. The prepared materials were successfully employed as host materials for green and red dopants in phosphorescent organic light emitting diodes. Thus, this work presents the first application of this novel linkage mode in the design and synthesis of functional π-conjugated organic donor–acceptor materials and their application in organic light emitting diodes.

9-(4-Bromo­phen­yl)-9H-carbazole

In the title molecule, C18H12BrN, the 4-bromophenyl ring is inclined to the mean plane of the carbazole moiety (r.m.s. devation = 0.027 Å) by 49.87 (5)°. In the crystal, molecules stack along [001] and are linked by C—H⋯π interactions forming a corrugated two-dimensional network lying parallel to (100).

1-Nitro-9H-carbazole

In the title molecule, C12H8N2O2, the nitro group is tilted slightly with respect to the carbazole moiety [angle between the least-squares planes = 4.43 (9)°]. In the crystal, the molecules are connected via pairs of N—H⋯O hydrogen bonds into dimers with -1 symmetry. The dimers in turn are arranged into layers parallel to (10-1).

The pseudo-inversion symmetry of 9,90′ (1,3,4-oxadiazole-2,5-diyldi(1,1′-biphenyl)-2′,4- diyl)bis[9H-carbazole] in the light of OD theory

Abstract The crystal structure of 9,9′-(1,3,4-oxadiazole- 2,5-diyldi(1,1′-biphenyl)-2′,4-diyl)bis[9H-carbazole] [Pna21, Z = 4, a = 17.9874 (4) Å, b = 9.2989 (8) Å, c = 21.5822 (9) Å, Robs = 0.0395, 9239 F data, 496 parameters] features a pseudo-centre of inversion strictly valid only for isolated layers of the structure. It is an order-disorder (OD) structure made up of one kind of non-polar layers composed of (I) molecules connected to polar layer pairs. The major polytype is of a maximum degree of order. The magnitude of the intrinsic translation vectors of the glides and screws relating adjacent layers is a convenient quantification of the deviation from perfect centrosymmetry.

Isotypic crystal structures of 2,6-di­bromo-N,N-bis­(4-nitro­phen­yl)aniline and 2,6-di­chloro-N,N-bis­(4-nitro­phen­yl)aniline

The central ternary N atoms in the isotypic crystal structures of the substituted anilines show no sign of pyramidalization.

OD- and non-OD-polytypism of 9-(3-chloropyridin-4-yl)-9H-carbazole

Abstract 9-(3-Chloropyridin-4-yl)-9H-carbazole (1) crystallizes as polytypes made up of layers of one kind with P(c)21b symmetry, in which layer contacts are geometrically non-equivalent (non-OD polytypes). In both polytypes adjacent layers are related by a glide reflection with a plane parallel to (100). In polytype I (Ic2a), the intrinsic translation vector of the glide reflection is b/2. In polytype II (P21), the intrinsic translation vector is sc/2 with s=0.771. It is a polytype with a maximum degree of order (MDO) of a family of OD structures. Fragments of the second MDO polytype lead to systematic twinning by reflection at (100). For crystals of both polytypes the absolute structure was determined [Flack parameters −0.03(5) and −0.05(5)]. Despite being of the non-OD type, the formalism of OD theory is applied to achieve a unified description of the symmetry of both polytypes.