Crystallographic data on certain sterically strained naphthacene derivatives

Akopyan, Z. A.; Avoyan, R. L.; Struchkov, Yu. T.

doi:10.1007/bf00753247

Cited by 11 publications

(11 citation statements)

References 2 publications

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“…Rubrene has three known polymorphs belonging to the triclinic, monoclinic, and orthorhombic crystal systems. , The triclinic and monoclinic forms are observed in solution-grown crystals, orthorhombic in vapor-grown, and orthorhombic and triclinic in annealed thin films, shown in Figure a–d.…”

Section: Resultsmentioning

confidence: 99%

Crystal Morphology and Growth in Annealed Rubrene Thin Films

Fielitz

Holmes

2016

Crystal Growth & Design

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While controlled crystallization of organic thin films holds great potential for enhancing the performance of electronic devices, quantitative understanding of the processes involved is limited. Here, we characterize the thin film crystal growth of the organic semiconductor rubrene during annealing using polarized optical microscopy with a heated stage for in situ measurements, followed by atomic force microscopy and X-ray diffraction. During annealing, the film undergoes transitions from predominant growth of a polycrystalline triclinic crystal structure to single crystal orthorhombic, followed by polycrystalline growth of the orthorhombic polymorph. Observation of crystal morphology with time allows determination of the crystal orientation, which is used in conjunction with crystal size measurements to determine the crystallization activation energies for the observed growth phases and crystal planes.

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Section: Resultsmentioning

confidence: 99%

Crystal Morphology and Growth in Annealed Rubrene Thin Films

Fielitz

Holmes

2016

Crystal Growth & Design

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“…Several polymorphs of rubrene have been reported. A monoclinic phase was described by Taylor (1936) and a triclinic polymorph was explored by Akopyan et al (1962). Unfortunately, these reports do not mention the growth method.…”

Section: Methodsmentioning

confidence: 99%

Low-temperature structure of rubrene single crystals grown by vapor transport

Jurchescu

Meetsma

Palstra

2006

Acta Crystallogr B Struct Sci

308

296

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“…It must be stressed here that rubrene doesn't exhibit an SIP, but it has been shown to have several different polymorphs and is an excellent example of the importance of crystal structure to device properties. Four different polymorphs of rubrene are found in the literature, a monoclinic phase, a triclinic form and two orthorhombic polymorphs. The first orthorhombic form, with space group Aba 2, was found for crystals grown from vapor in a vacuum using sealed ampoules .…”

Section: Experimentally Observed Sipsmentioning

confidence: 99%

Substrate‐Induced and Thin‐Film Phases: Polymorphism of Organic Materials on Surfaces

Jones

Chattopadhyay

Geerts

et al. 2016

Adv Funct Materials

231

280

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2233wileyonlinelibrary.com to that of the bulk liquid; [ 7 ] order typically exists over a few molecular layers before rapidly decaying to bulk behavior as the distance from the wall increases. [ 8 ] Similar ordering effects can also be observed in the quasiliquids which form on the surface of many solids due to surface melting (also known as premelting): [ 9,10 ] the existence of a liquid-like layer a few molecules thick on the surface of a solid below the melting point of the bulk material. [ 11 ] The structure within this layer is also found to be different to that of the bulk isotropic liquid, [ 12 ] highlighting the ordering occurring at the interface. A converse effect, surface freezing, is also observed in some liquids (primarily n -alkanes with 16 ≤ n ≤ 50), where a solid monolayer may exist at an interface up to ≈30 °C above the bulk melting point while the rest of the compound is molten. [13][14][15] Such phase behavior is strongly dependent on molecular shape and has only been observed for chain molecules, which then form layers similar to self-assembled monolayers (SAMs) at the interface with the liquid bulk. [ 16 ] Further examples of molecular ordering at interfaces can be seen in materials which display liquid crystal (LC) phases, a phase behavior also dependent on molecular shape and generally observed for molecules with a highly anisotropic shape (e.g., rod-like, disc-like or bowl-like molecules). [ 17 ] LCs have properties of both solids and liquids and display long range order which may be orientational and/or positional; various types of LC phases (mesophases) are possible and normally exist only over a certain temperature range (i.e., they are thermotropic); a further property of LCs is that they generally reach thermodynamic equilibrium in the bulk and at interfaces as a result of their short relaxation time. Nematic (N) phases of calamitic LCs (rod-like molecules with cylindrical symmetry) have no positional order but an orientational order which can be described by a unit vector, n , known as the director, which represents the preferred molecular orientation ( Figure 1 , left). A scalar order parameter can also be defi ned which is related to the average angle the long molecular axes make to the director, n .Increased order is seen in smetic phases (Sm) which have both orientational and positional order; for example in a smetic A phase (SmA) molecules form layers (positional ordering of the molecular mass centers) which are oriented normal to the plane of the layers (orientational order), while smetic C phases (SmC) form layers where molecules are oriented with the long molecular axes tilted at an angle to the molecular layer normal However, the factors that drive such a process are not clearly understood or studied in depth. In this feature article, we review the current state of understanding concerning SIPs, giving examples of systems where SIPs have been observed, discussing their origins, and which questions remain to be answered. The role of the substrate in controlling the growth a...

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Crystallographic data on certain sterically strained naphthacene derivatives

Cited by 11 publications

References 2 publications

Crystal Morphology and Growth in Annealed Rubrene Thin Films

Crystal Morphology and Growth in Annealed Rubrene Thin Films

Low-temperature structure of rubrene single crystals grown by vapor transport

Substrate‐Induced and Thin‐Film Phases: Polymorphism of Organic Materials on Surfaces

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