The title compound, C(35)H(36)N(4)O(4), was prepared as a spiro-lactam ring formation of rhodamine B dye for comparison with a ring-opened form. The xanthene ring system is approximately planar. The r.m.s. deviation from planarity is 0.064 (6) Å for the xanthene ring. The dihedral angles formed by the spiro-lactam and 2,4-dihydroxy-benzene rings with the xanthene ring system are 86.6 (9) and 88...

The title compound, C(36)H(36)N(4)O(4), was prepared as a spiro-lactam ring formation of the rhodamine dye for comparison with a ring-opened form. The xanthene ring system is approximately planar [r.m.s. deviations from planarity = 0.023 (9) Å for the xanthene ring]. The dihedral angles formed by the spiro-lactam and 1,3-benzodioxole rings with the xanthene ring system are 86.8 (1) and 74.3 (1)...

In the title compound, C(26)H(25)FO(5), the terminal cyclo-hexane rings of the xanthene ring system adopt half-boat conformations. The 4H-chromene ring make a dihedral angle of 87.94 (5)° with the xanthene ring system and its carbonyl O atom lies above the xanthene O atom. In the crystal, mol-ecules are linked into ribbons propagating along the a-axis direction by C-H⋯O hydrogen bonds. Aromatic...

In the xanthene ring system in the title compound, C19H18O4, the 4H-pyran ring has a maximum deviation of 0.110 (2) Å from planarity and the cyclo-hexene ring exhibits a puckered conformation [puckering parameters Q T = 0.452 (3) Å, θ = 57.0 (4) and ϕ = 131.7 (4)°]. The cyclo-hexene ring attached to the xanthene system adopts an envelope conformation, with the middle of the three methylene C at...

The title compound, C(35)H(35)ClN(4)O(3), resulted from a spiro-lactam ring closure of rhodamine B dye. The xanthene ring system is approximately planar [r.m.s. deviation = 0.050 (9) Å for the xanthene ring]. The dihedral angles formed by the spiro-lactam and 5-chloro-2-hy-droxy-benzene rings with the xanthene ring system are 87.9 (7) and 79.1 (7)°, respectively.

In the title compound, C(27)H(15)Br(2)ClO·C(3)H(7)NO, the xanthene moiety has a flattened boat conformation with a folding angle between the naphthalene units of 9.46 (3)°. The mean planes of the xanthene system and its 4-chloro-phenyl substituent are nearly perpendicular [dihedral angle = 89.43 (5)°]. The dimethyl-formamide solvent mol-ecule is disordered over two sets of sites with an occupan...

Xanthene dyes can be appended to cyclodextrins via an ester or amide bridge in order to switch the fluorescence on or off. This is made possible through the formation of nonfluorescent lactones or lactams as the fluorophore can reversibly cyclize. In this context we report a green approach for the synthesis of switchable xanthene-dye-appended cyclodextrins based on the coupling agent 4-(4,6-dim...

In the xanthene ring system of the title compound, C(23)H(25)BrO(4), the 4H-pyran ring is almost planar [maximum deviation = 0.040 (3) Å] and the cyclo-hexene ring adopts a sofa conformation. The cyclo-hexene ring attached to the xanthene system is puckered [Q(T) = 0.427 (3) Å, θ = 55.0 (4) ° and ϕ = 164.4 (6) °]. In the crystal, mol-ecules are linked to each other by O-H⋯O and C-H⋯O hydrogen b...

In the title compound, C(37)H(40)N(4)O(2), the xanthene and spiro-lactam rings are almost planar, with r.m.s. deviations from the mean planes of 0.223 (2) and 0.057 (2) Å, respectively, and form a dihedral angle of 85.76 (3)°. The dihedral angle between the xanthene mean plane and the benzene ring is 87.16 (5)°. One of the two ethyl groups of one of the diethyl-amino groups is disordered over t...

Enoate reductases from the family of old yellow enzymes (OYEs) can catalyze stereoselective trans-hydrogenation of activated C=C bonds. Their application is limited by the necessity for a continuous supply of redox equivalents such as nicotinamide cofactors [NAD(P)H]. Visible light-driven activation of OYEs through NAD(P)H-free, direct transfer of photoexcited electrons from xanthene dyes to th...