cis-Thioindigo (TI) - a new ligand with accessible radical anion and dianion states. Strong magnetic coupling in the {[TI-(μ2-O),(μ-O)]Cp*Cr}2 dimers

On-Surface Isomerization of Indigo within 1D Coordination Polymers

Natural products are attractive components to tailor environmentally friendly advanced new materials. We present surface-confined metallosupramolecular engineering of coordination polymers using natural dyes as molecular building blocks: indigo and the related Tyrian purple. Both building blocks yield identical, well-defined coordination polymers composed of (1 dehydroindigo : 1 Fe) repeat units on two different silver single crystal surfaces. These polymers are characterized atomically by submolecular resolution scanning tunnelling microscopy, bond-resolving atomic force microscopy and X-ray photoelectron spectroscopy. On Ag(100) and on Ag(111), the trans configuration of dehydroindigo results in N,O-chelation in the polymer chains. On the more inert Ag(111) surface, the molecules additionally undergo thermally induced isomerization from the trans to the cis configuration and afford N,N- plus O,O-chelation. Density functional theory calculations confirm that the coordination polymers of the cis-isomers on Ag(111) and of the trans-isomers on Ag(100) are energetically favoured. Our results demonstrate post-synthetic linker isomerization in interfacial metal-organic nanosystems.

Structure and properties of radical anion and dianion salts of organic dye trans-perinone and its mixed salt with gallium(iii) phthalocyanine

Reduction of organic dye trans-perinone in different experimental conditions was studied. New crystallite salts containing reduced species of trans-perinone together with mixed salt with Ga^IIIClPc radical anions were obtained and characterized.

Strong magnetic coupling of spins in Fe(ii) dimers with differently charged thioindigo ligands

A first coordination {[2.2.2]cryptand(K+)}2{FeII(TI˙-)(TI2-)}2·2C6H4Cl2 (1) complex of iron(ii) containing radical anions and dianions of thioindigo (TI) was obtained. The complex has two high-spin FeII centers bound by two oxygen atoms, and the TI˙- radical anions are coordinated to each FeII. As a result, the 4-spin system consisting of TI˙- (S = 1/2)-FeII (S = 2)-FeII (S = 2)-TI˙- (S = 1/2) coupled spins is formed within a dimer with strong FeII-FeII (J = -51.1 cm-1) and weaker FeII-TI˙- interactions of (J = -35.4 cm-1).

Flavanthrone – a new ligand with accessible radical anion and dianion states: preparation of zwitterionic {(Cp2V)2(flavanthrone)} and {(Cp2V)2(chloranil)} complexes

Molecular structure, optical and magnetic properties of the radical anions and dianions of flavanthrone dye are presented. Flavanthrone and chloranil coordinate two vanadocenes forming zwitter-ionic {(Cp₂V⁺)₂(Flavanthrone²⁻)} and {(Cp₂V⁺)₂(QCl₄²⁻)}.

Optical and magnetic properties of trans-indigo˙− radical anions. Magnetic coupling between trans-indigo˙− (S = 1/2) mediated by intermolecular hydrogen N–H⋯OC bonds

Reduction of trans-indigo yields salt {cryptand[2.2.2](K⁺)}₆{trans-indigo}₇·5.5C₆H₄Cl₂ (1). The trans-indigo˙⁻ radical anions are bonded by intermolecular hydrogen N–H⋯OC bonds of 2.11–2.17 Å.

Coordination Complexes of Titanium(IV) and Indium(III) Phthalocyanines with Carbonyl-Containing Dyes: The Formation of Singly Bonded Anionic Squarylium Dimers

Reduction methods for the preparation of coordination complexes of titanium(IV) and indium(III) phthalocyanines (Pc) with organic dyes such as indigo, thioindigo, and squarylium dye III (SQ) have been developed, which allow one to obtain crystalline {cryptand(K⁺ )}{(cis-indigo-O,O)^2- Ti^IV (Pc^2- )}(Cl^- )⋅C₆ H₄ Cl₂ (1), {cryptand(K⁺ )}{(cis-thioindigo-O,O)^2- In^III (Pc^2- )}^- ⋅C₆ H₄ Cl₂ (2), and {cryptand(K⁺ )}{[(SQ)₂ -O,O]^2- In^III (Pc^2- )}^- ⋅3.5 C₆ H₄ Cl₂ (3) complexes. The formation of these complexes is accompanied by the reduction of the starting dyes to the anionic state. Transition of trans-indigo or trans-thioindigo to the cis conformation in 1 and 2 provides coordination of both carbonyl oxygen atoms of the dye to Ti^IV Pc or In^III Pc. SQ is reduced to the radical anion state and forms unusual diamagnetic singly bonded (SQ^- )₂ dimers in 3. These dimers have two closely positioned carbonyl oxygen atoms coordinated to In^III Pc. Dianionic Pc^2- macrocycles have been found in 1-3. The complexes contain two chromophore molecules at one metal center. However, their optical spectra are defined mainly by absorption bands of the metal phthalocyanines.

Reaction of tin(iv) phthalocyanine dichloride with decamethylmetallocenes (M = CrII and CoII). Strong magnetic coupling of spins in (Cp*2Co+){SnIVCl2(Pc˙3-)}˙-·2C6H4Cl2

The reaction of tin(iv) phthalocyanine dichloride {Sn^IVCl₂(Pc^2-)} with decamethylmetallocenes (Cp*₂M, M = Co, Cr) has been studied. Decamethylcobaltocene reduces Sn^IVCl₂(Pc^2-) to form the (Cp*₂Co⁺){Sn^IVCl₂(Pc˙^3-)}˙^-·2C₆H₄Cl₂ (1) complex. The negative charge of {Sn^IVCl₂(Pc˙^3-)}˙^- is delocalized over the Pc macrocycle providing the alternation of the C-N(imine) bonds, the appearance of new bands in the NIR range and a strong blue shift of both the Soret and Q-bands in the spectrum of 1. The magnetic moment of 1 is equal to 1.68μ_B at 300 K, indicating the contribution of one S = 1/2 spin of the Pc˙^3- macrocycles. These macrocycles form closely packed double stacks in 1 with effective π-π interactions providing strong antiferromagnetic coupling of spins at a Weiss temperature of -80 K. Decamethylchromocene initially also reduces Sn^IVCl₂(Pc^2-) to form the [(Cp*₂Cr⁺){Sn^VICl₂(Pc˙^3-)}˙^- complex but further reaction between the ions is observed. This reaction is accompanied by the substitution of one Cp* ligand of Cp*₂Cr by chloride anions originating from {Sn^IVCl₂(Pc˙^3-)}˙^- to form the complex {(Cp*CrCl₂)(Sn^IV(μ-Cl)(Pc^2-))}·C₆H₄Cl₂ (2) in which the (Cp*CrCl₂) and {Sn^IV(Pc^2-)} species are bonded through the μ-bridged Cl^- anion. According to the DFT calculations, this reaction proceeds via an intermediate [(Cp*₂CrCl)(SnClPc)] complex.

Interligand Charge Transfer in a Complex of Deprotonated cis-Indigo Dianions and Tin(II) Phthalocyanine Radical Anions with Cp*IrIII

A diamagnetic complex, {(cis-indigo-N,N)^2-(Cp*Ir^III)} (1), in which deprotonated cis-indigo dianions coordinate an iridium center through two nitrogen atoms was obtained. By employment of the ability of the iridium center in 1 to coordinate an additional ligand, the complex [(Bu₄N⁺)₂{[Sn^II(Pc^•3-)](cis-indigo-N,N)^2-Cp*Ir^III}^•-₂·0.5(H₂Indigo)·2.5C₆H₄C_l2 (2), which has two functional ligands coordinating an Ir^III center, was obtained. This complex has a magnetic moment of 1.71 μ_B at 300 K, in accordance with an S = 1/2 spin state. The spin density is mainly delocalized over the Pc^•3- macrocycle and partially on (cis-indigo-N,N)^2-. Due to an effective π-π interaction, a thermally activated charge transfer from [Sn^II(Pc^•3-)]^•- to (cis-indigo-N,N)^2- is observed, with an estimated Gibbs energy (-ΔG°) of 9.27 ± 0.18 kJ/mol. The deprotonation of indigo associated with the coordination of Ir^III by the indigo releases H⁺ ions, which protonate noncoordinating indigo molecules to produce leuco cis-indigo (H₂Indigo). One H₂indigo links two (cis-indigo-N,N)^2- dianions in 2 to produce strong N-H···O═C and O-H···O═C hydrogen-bonding interactions.