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Crystal structure of 2-(thiophen-3-yl)ethyl pyrene-1-carboxylate

In the title compound, C23H16O2S, the thiophene group is rotationally disordered into two fractions almost parallel to each other, with occupation factors of 0.523 (7) and 0.477 (7), and subtending dihedral angles of 10.5 (5) and 9.3 (5)°, respectively, to the thiophene group. The molecules are held together by weak C—H⋯O and C—H⋯π hydrogen bonds, producing a laminar arrangement, which are further connected in a perpendicular fashion by S⋯π contacts [S⋯centroid = 3.539 (8) and 3.497 (8) Å]. In spite of the presence of the entended pyrene group, the structure does not present any parallel π–π stacking interactions. The structure was refined as an inversion twin.


S1. Chemical context
Pyrene and their derivatives are well-known for their optical and electronic properties (Hrdlovič & Lukáč, 2000;Winnik 1993). They exhibit long fluorescence lifetimes in non-polar media (ca. 400 ns) in addition to their ability to form homo and hetero-dimmers in excited states (excimers, exciplexes) (Kim et al., 2008). The photophysical properties of pyrene derivatives can be used as sensor for oxygen (Basu & Rajam, 2004) and as monitor for polymerization reactions (Chmela et al., 2005). The fluorescence studies of pyrenes as sensor are based in processes of electron transference, changes of wavelength of higher emission and the formation of excited states (excimers, exciplexes).
The preparation of thiophene derivatives with fluorescent properties has been studied in order to obtain polythiophenes.
The polymers of thiophenes are a class of linear conjugated polymers characterized by their versatility and are used as materials for electronic and optoelectronic applications (Perepichka et al.,2005) (Abd-El- Aziz et al., 2013).
In this context, we present the crystal structure of a pyrene functionalized with a thiophene moiety.

S2. Structural commentary
The molecular structure of the title compound is shown in Fig. 1. The compound shows rotational disorder at the thiophene group into two planar, almost parallel moieties (See Refinement section). The thiophene ring presents a trans configuration with respect to the carboxylatepyrene group with a torsion angle C14-C13-C12-O2 of -170.9 (3) °.
Bond distances are in agreement with those reported for similar organic compounds (Allen et al., 1987).

S3. Supramolecular features
Based on the distances obtained using PLATON (Spek, 2009), the crystal packing is the result of weak C-H···O and C-H···π intermolecular interactions, reported in Table 2 and shown in Fig 2, which define laminar arrangements (Fig 3).

S4. Database survey
We reported previously the crystal structure of 1-methoxypyrene (Morales-Espinoza et al.,2015) where the crystal packing is governed by π-π and C-H···π interactions. A search of the Cambridge Structural Database (CSD, CSD version 5.36 updates Nov 2014) with 1-carboxylate skeleton affords eight organic hits, but none with a thiophene group.

S6. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 1. The H atoms were included in calculated positions and treated as riding: C-H = 0.93 Å for aromatic H's and C-H= 0.97 for methylene ones. Uiso(H) = 1.2Ueq(C). The rotational disorder of the thiophene group was modelled with a couple of split positions (S1-C17 and S1A-C17A), with an occupation ratio of 0.523 (7)/0.477 (7). Similarity restraints in distances and displacemnent factors were used for modelling the disordered fraction. The crystals were poorly diffracting, which led to a high Rint.

Figure 1
The molecular structure of the title compound, showing the atom labelling. Displacement ellipsoids are drawn at the 30% probability level. Only the major fraction of the disordered thiophene has been drawn.

Figure 4
Representation of the S···π interaction (Only major fraction of the disordered thiophene group). Hydrogen atosm omitted.