UV crosslinked poly(acrylic acid): a simple method to bio-functionalize electrolyte-gated OFET biosensors.

A simple and time-saving wet method to endow the surface of organic semiconductor films with carboxyl functional groups is presented. A thin layer of poly(acrylic acid) (pAA) is spin-coated directly on the electronic channel of an electrolyte-gated organic FET (EGOFET) device and cross-linked by UV exposure without the need for any photo-initiator. The carboxyl functionalities are used to anchor phospholipid bilayers through the reaction with the amino-groups of phosphatidyl-ethanolamine (PE). By loading the membranes with phospholipids carrying specific functionalities, such a platform can be easily implemented with recognition elements. Here the case of biotinylated phospholipids that allow selective streptavidin electronic detection is described. The surface morphology and chemical composition are monitored using SEM and XPS, respectively, during the whole process of bio-functionalization. The electronic and sensing performance level of the EGOFET biosensing platform is also evaluated. Selective analyte (streptavidin) detection in the low pM range is achieved, this being orders of magnitude lower than the performance level obtained by the well assessed surface plasmon resonance assay reaching the nM level, at most.

6a-Nitro-6-(2,2,7,7-tetra-methyl-tetra-hydro-3aH-bis-[1,3]dioxolo[4,5-b:4',5'-d]pyran-5-yl)-6a,6b,7,8,9,11a-hexa-hydro-6H-spiro-[chromeno[3,4-a]pyrrolizine-11,11'-indeno-[1,2-b]quinoxaline].

In the title compound, C39H38N4O8, the quinoxaline and indene subunits are essentially planar, with maximum deviations of 0.071 (2) and 0.009 (2) Å, respectively. The indeno-quinoxaline system forms a dihedral angle of 72.81 (3)° with the chromenopyrrolizine system. The two dioxolane rings, as well as the pyran ring of the chromeno group and the terminal pyrrolizine, each adopt an envelope conformation with O and C as flap atoms. The central pyrrolizine ring adopts a twisted conformation. Intra-molecular C-H⋯O and C-H⋯N hydrogen bonds occur. The crystal structure exhibits C-H⋯O hydrogen bonds, and is further stablized by C-H⋯π inter-actions, forming a two-dimensional network along the bc plane.

Methyl 3'-benzyl-4'-(2-chloro-phen-yl)-1'-methyl-2-oxo-spiro-[indoline-3,2'-pyrrolidine]-3'-carboxyl-ate.

In the title compound, C27H25ClN2O3, the methyl-pyrrolidine ring adopts an envelope conformation with the N atom at the flap. The mean plane of the pyrrolidine ring makes dihedral angles of 82.1 (1), 84.4 (1) and 79.8 (1)°, respectively, with the adjacent benzene ring, the mean plane of the indoline ring system and the phenyl ring. The mol-ecular structure is stabilized by intra-molecular C-H⋯O hydrogen bonds. In the crystal, mol-ecules are linked into chains along [101] by N-H⋯O hydrogen bonds. C-H⋯π inter-actions are observed between the chains.

2-Ferrocenyl-3-nitro-2H-chromene.

In the title compound, [Fe(C5H5)(C14H10NO3)], the cyclo-penta-dienyl rings are in an eclipsed conformation and the pyran ring adopts a half-chair conformation. The mean plane of the pyran ring makes dihedral angles of 79.33 (1) and 80.73 (1)°, respectively, with the substituted and unsubstituted cyclo-penta-dienyl rings. In the crystal, pairs of C-H⋯O hydrogen bonds link the mol-ecules into inversion dimers with R 2 (2)(16) motifs.

Dimethyl 1,8-bis-(4-methyl-phen-yl)-11-oxatri-cyclo-[6.2.1.0(2,7)]undeca-2,4,6,9-tetra-ene-9,10-di-carboxyl-ate.

The title compound, C28H24O5, consists of a fused tricyclic system containing two five-membered rings and one six-membered ring. The five-membered rings both exhibit an envelope conformation with the O atom at the flap, whereas the six-membered ring adopts a boat conformation. The dihedral angle between the 4-methyl-phenyl rings at the 1,8-positions is 76.4 (1)°. In the crystal, mol-ecules are stacked in columns along the a axis through C-H⋯O inter-actions.

Methyl 2-[(2-chloro-quinolin-3-yl)(hy-droxy)meth-yl]acrylate.

There are two independent mol-ecules (A and B) in the asymmetric unit of the title compound, C14H12ClNO3. The mean planes of the methyl ester unit (Cmeth-yl-O-C=O; r.m.s. deviation = 0.051 Šfor mol-ecule A and 0.016 Šfor mol-ecule B) and the chloro-quilonine ring system (r.m.s. deviation = 0.023 Šfor mol-ecule A and 0.014 Šfor mol-ecule B) form dihedral angles of 63.5 (1)° in mol-ecule A and 78.1 (1)° in mol-ecule B. The main difference between the two independent mol-ecules is reflected in the (H)O-C-C=C(H2) torsion angle which is -109.7 (2)° in mol-ecule A and 10.6 (2)° in mol-ecule B. An intra-molecular O-H⋯O hydrogen bond is observed in mol-ecule A. In the crystal, mol-ecules A and B are linked into pairs via bifurcated O-H⋯(N,Cl) hydrogen bonds and a weak C-H⋯O hydrogen bond links pairs of mol-ecules into chains along [100].

rac-Methyl 3-(2-meth-oxy-phen-yl)-3a,4-di-hydro-3H-chromeno[4,3-c]isoxazole-3a-carboxyl-ate.

The title compound, C19H17NO5, comprising two stereogenic C atoms of the same configuration, crystallizes in a centrosymmetric space group as a racemate. The pyran ring adopts a half-chair conformation, while the isoxazole ring adopts an envelope conformation with the C atom bonded to the meth-oxy-phenyl group as the flap. The dihedral angle between the mean plane of the pyran ring and the adjacent benzene ring is 5.86 (5)°. In the crystal, mol-ecules are linked by a weak C-H⋯O hydrogen bond, forming a chain along the a axis.

rac-3-(4-Chloro-phen-yl)-3a,4-di-hydro-3H-chromeno[4,3-c]isoxazole-3a-carbo-nitrile.

The title compound, C17H11ClN2O2, which contains two stereogenic C atoms, crystallizes in a centrosymmetric space group as a racemate. The pyran ring and the isoxazole ring adopt sofa and twisted conformations, respectively. The dihedral angle between the benzene ring and the mean plane through the near coplanar atoms of the pyran ring is 4.17 (5)°. The mol-ecular conformation features a weak C-H⋯O contact. In the crystal, C-H⋯O hydrogen bonds link the mol-ecules, forming chains along the a-axis direction.

2-[(2-Chloro-quinolin-3-yl)(hy-droxy)meth-yl]acrylo-nitrile.

In the title compound, C13H9ClN2O, the dihedral angle between the acrylo-nitrile C=C-CN plane and the quilonine ring system is 71.3 (2)°. In the crystal, mol-ecules are linked by O-H⋯N hydrogen bonds, forming chains along [01-1]. The chains are linked into a three-dimensional network through C-H⋯N inter-actions.

5-(3-Meth-oxy-phen-yl)-3-phenyl-1,2-oxazole.

In the title compound, C16H13NO2, the isoxazole ring makes dihedral angles of 17.1 (1)° with the 3-meth-oxy-phenyl ring and 15.2 (1)° with the phenyl group. Centrosymmetric dimers that are realised by pairs of C-H⋯π inter-actions are observed in the crystal structure.

(E)-1-Ferrocenyl-3-[2-(2-hy-droxy-eth-oxy)phen-yl]prop-2-en-1-one.

In the title compound, [Fe(C5H5)(C16H15O3)], the cyclo-penta-dienyl rings are in an eclipsed conformation and the benzene ring makes dihedral angles of 10.84 (9) and 12.35 (9)°, respectively, with the substituted and unsubstituted cyclo-penta-dienyl rings. In the crystal, mol-ecules form inversion dimers through pairs of O-H⋯O hydrogen bonds. Weak C-H⋯O hydrogen bonds are observed between the dimers.

Diethyl 1,8-diphenyl-11-oxatricyclo-[6.2.1.0(2,7)]undeca-2,4,6-triene-9,10-dicarboxyl-ate.

The title compound, C28H26O5, is the Diels-Alder adduct from 1,3-diphenyl-benzo[c]furan and diethyl maleate. The mol-ecule comprises of a fused tricyclic system containing two five-membered rings, which are in envelope conformations with the O atom at the flap, and a six-membered ring adopting a boat conformation. The dihedral angle between phenyl substituents in the 1,8-positions is 55.1 (1)°. The ethyl groups are disordered over two sets of sites, with occupancy ratios of 0.648 (9):0.352 (9) and 0.816 (1):0.184 (1). In the crystal, pairs of C-H⋯π inter-actions link the mol-ecules into inversion dimers.

1-(4-{2-[(E)-3-(4-Chloro-phen-yl)-3-oxo-prop-1-en-1-yl]phen-oxy}but-yl)-1H-indole-3-carbaldehyde.

In the title compound, C(28)H(24)ClNO(3), the dihedral angles between the central benzene ring and the indole ring system and the chlorobenzene ring are 70.81 (5) and 78.62 (5)°, respectively. The mol-ecular structure is stabilized by a weak intra-molecular C-H⋯O inter-action. In the crystal, pairs of C-H⋯O hydrogen bonds link the mol-ecules into inversion dimers with an R(2) (2)(14) motif.

rac-Methyl 3-(2-meth-oxy-phen-yl)-1-phenyl-3,3a,4,9b-tetra-hydro-1H-chromeno[4,3-c]isoxazole-3a-carboxyl-ate.

The title compound, C(25)H(23)NO(5), comprising two stereogenic carbon atoms of the same configuration, crystallizes in a centrosymmetric space group as a racemate. The six-membered pyran ring and the five-membered isoxazole ring adopt sofa and twisted conformations, respectively. The dihedral angle between the benzene ring and the mean plane through the near coplanar atoms of the pyran ring is 10.73 (7)°. The crystal structure features C-H⋯O hydrogen bonds.

rac-6-Eth-oxy-3,3a,4,9b-tetra-hydro-1,3-diphenyl-1H-chromeno[4,3-c]isoxazole-3a-carbonitrile.

The title compound, C(25)H(22)N(2)O(3), with three stereogenic centres, crystallizes in a centrosymmetric space group as a racemate. The pyran ring adopts a sofa conformation and the five-membered isoxazole ring exhibits an envelope conformation. The dihedral angle between the benzene ring and the mean plane through the near coplanar atoms of the pyran ring is 10.54 (9)°. In the crystal, no significant intermolecular interactions are observed.

Methyl (E)-2-[(2-nitro-phen-oxy)meth-yl]-3-phenyl-acrylate.

The title compound, C(17)H(15)NO(5), adopts an E conformation with respect to the C=C double bond of the phenyl-acrylate unit. The phenyl ring and methyl acrylate group of the phenyl-acrylate unit are disordered over two sets of sites with site-occupancy ratios of 0.705 (5):0.295 (5) and 0.683 (3):0.317 (3), respectively. The mean plane through the benzene ring of the phenyl acrylate makes dihedral angles of 88.4 (8) (major component) and 86.7 (8)° (minor component) with the nitro-phen-oxy ring; the dihedral angle between the two components is 3.64 (6)°. Intra-molecular C-H⋯O interactions stabilise the molecular structure. In the crystal, C-H⋯O inter-actions result in a chain of mol-ecules running along the b axis.

3-(1,2-Di-p-tolyl-vin-yl)-2-methyl-1H-indole.

In the title compound, C(25)H(23)N, the indole unit makes a dihedral angles of 79.03 (5) and 61.82 (4)° with the benzene rings. No classical hydrogen bonds are found in the crystal structure.

(E)-3-Phenyl-2-(1-tosyl-1H-indol-3-ylcarbon-yl)acrylonitrile.

In the title compound, C(25)H(18)N(2)O(3)S, the indole moiety is planar and makes a dihedral angle of 89.95 (09)° with the phenyl ring of the sulfonyl substituent. The mol-ecular conformation features a weak C-H⋯N short contact and the crystal packing reveals a weak C-H⋯O hydrogen bond.

2-Iodo-3-(4-meth-oxy-anilino)-5,5-dimethyl-cyclo-hex-2-en-1-one.

The cyclo-hexene ring in the title compound, C(15)H(18)INO(2), adopts a sofa conformation. The dihedral angle between the cyclo-hexene (through all ring atoms) and benzene rings is 63.3 (1)°. The mol-ecular conformation features an N-H⋯I short contact and the crystal packing features C-H⋯O hydrogen bonds.