1,1',5,5'-tetramethyl-6,6'-dioxobis(verdazyl) (BVD) reacts with copper(I) halides in acetonitrile and copper(II) methanol to give coordination polymers of composition [Cu2X2(BVD)]x. When X = Cl Br, these crystallize orthorhombic unit cells dimensions a 6.684(1) Å, b 12.524(3) c 8.717(2) Å (X Cl) 12.680(2) 6.744(1) 8.822(2) Br). With I, powder diffraction indicates monoclinic cell 12.669 8.461 7.679 β 91.88°, although poor crystal quality prevented full structure determination. Magnetic...

The 3-(2'-imidazolyl)-1,5-dimethyl-6-oxoverdazyl radical (imvd(*)) and the corresponding tetrazane H3imvd were prepared structurally characterized, former as two different hydrates. Reaction of imvd(*) with [M(hfac)2] led to formation monometallic complexes [M(hfac)2(imvd(*))] (M = Ni Mn). They characterized by single-crystal X-ray diffraction. In solid state, all four radical-containing compounds exhibit imidazole-oxoverdazyl pi stacking. Following structural analysis, behaves an...

1,5-Diisopropyl-6-oxo-verdazyl free radicals were synthesized via the condensation of BOC protected isopropyl hydrazine with phosgene, deprotection aqueous HCl, aldehydes to form tetrazanes and finally oxidation give radicals. The introduction groups results in that show greater solubility a variety solvents are more stable than their methyl substituted counterparts. ESR shows reduced hyperfine coupling methine hydrogens consistent this hydrogen being plane verdazyl ring.

The past 17 years have seen the growth of coordination chemistry verdazyls—stable free radicals first reported in 1963. Though verdazyls are weakly basic ligands, ability to synthesize derivatives with chelating substituents, along steric similarity aromatic azine has resulted a variety compounds. Coordination compounds been Mn2+, Co2+, Ni2+, Cu+, Cu2+, Zn2+, Ru2+, Ag+, Cd2+, Tb3+, Dy3+, Gd3+ and Hg2+. These studies observations strong ferromagnetic exchange (up 400 cm−1), ligand-based redox...

Ferricyanide oxidation of 1,4,5,6-tetrahydro-2,4-dimethyl-6-(2'-pyridyl)-1,2,4,5-tetrazin-3(2H)-one (pvdH3) produces the stable chelating free radical 1,5-dimethyl-3-(2'-pyridyl)-6-oxoverdazyl (pvd) as an orange solid. Combination group 12 metal halides with ligand pvdH3 in acetonitrile results precipitation complexes. The mercuric chloride complex crystallizes monoclinic space P2(1/c) unit cell dimensions a = 8.5768(8) A, b 19.1718(17) c 8.5956(8) beta 90.405 degrees, and V 1413.4(2) A3....

Abstract We describe the self‐assembly processes as well structural and physico‐chemical properties of [2×2]Zn 2+ 4 grid complexes involving bis‐tridentate ligands 7 – 12 , based on bis(hydrazone)pyrimidine complexation subunits octahedrally coordinated Zn ions. The NMR spectroscopic data X‐ray crystal structure results indicate that in solution solid state 13 18 adopt a very compact arrangement providing stable [2×2] hydrazone‐grid arrays. π–π stacking between phenyl ring hydrazone units...

Substitution of the 3 position 6-oxoverdazyl free radicals with electron-rich arylamines, phenols, and aryl ethers elicits changes in UV-vis spectra pK(a) substituents consistent verdazyl being electron withdrawing. The is decreased: 80% methanol phenols 3a 3b have 10.4 10.9, respectively, while ammonium ion from protonation 3j has = 2.4. On basis these measurements, Hammett parameters for been estimated: sigma(p)(-) +0.48 sigma(m) +0.27. longest wavelength band visible spectrum red-shifted...

A new 1,5-dipyridyl verdazyl, synthesized from the corresponding dipyridyl hydrazone, coordinates nickel(II) to form a structurally characterized, pseudooctahedral complex analogous Ni(terpy)22+. The unusually short Ni–verdazyl distance results in strong ferromagnetic exchange (JNi–rad = +300, Jrad–rad +160 cm−1) between all three paramagnetic species along with metal–ligand charge transfer band electronic spectrum.

The diradical 1,1',5,5'-tetramethyl-6,6'-dioxo-3,3'-biverdazyl, 6, crystallizes in a monoclinic unit cell with = 4.224(1), b 17.378(2), c 7.529(1) Å, β 96.02(1)°, space group P21/c (No. 14). crystal structure of 6 shows local D2h symmetry. ESR measurements frozen chloroform solution indicate that isolated has singlet ground state triplet excited 760 cm-1 (0.094 eV) above the zero-field splitting parameters D 0.038 and E 0.0016 cm-1. Semiempirical calculations (AM-1) suggest is twisted...

A single electron reduction of an iron bis(verdazyl) complex results in a large change spin multiplicity resulting from combination crossover and exceptionally strong ferromagnetic exchange.

A cobalt bis(verdazyl) compound provides a new example of valence tautomerism in acetonitrile solution though the molecule is trapped ‘high energy’ tautomer crystalline material.

The diamagnetic iron(II) complexes of the hydrazone ligand pyridinecarboxaldehyde-2'-pyridylhydrazone (papyH) have been characterized by NMR, IR, UV-vis, and electrochemistry. dication Fe(papyH)(2)(2+) undergoes reversible one-electron oxidation at 0.66 V vs internal ferrocene shows a strong metal-ligand charge-transfer band in visible region 524 nm. Deprotonation with NaOH gives diamagnetic, neutral Fe(papy)(2) an potential -0.25 603 reacts active alkylating agents to give dialkyl...

A copper(I) complex of a 3-(6′-isopropylpyridyl)-substituted verdazyl was synthesized and characterized by X-ray crystallography magnetic susceptibility. The crystallizes in the monoclinic space group C2/c with cell dimensions = 22.544 Å, b 11.576 c 17.157 β 123.907°, V 3716.2 Å3. coordination geometry at copper is distorted tetrahedral, two ligand planes separated 75°. Magnetic susceptibility measurements indicate that ground state diradical triplet this geometry. Fitting to simple...

Halogenated 3‐aryl‐1,5‐diisopropyl verdazyl radicals have been shown to undergo Suzuki–Miyaura coupling reactions with a variety of boronic acids give biaryl‐substituted derivatives in acceptable good yields (50–90 %). The successful depends on the halo substituent and acid, but most could be coupled iodophenyl radical under either ligandless conditions or presence triphenylphosphine. palladium‐catalyzed reaction facilitates incorporation moieties into conjugated systems can used modify...

Three analogues of the 1,4-dihydropyrazine, 3,4,7,8-tetrahydro-4,4,8,8-tetramethyl-2,6-dioxa-4a,8a-diazaanthracene-1,5-dione (DDTTA), have been synthesized. 2,4,4,6,8,8-Hexamethyl-3,4,7,8-tetrahydro-2,4a,6,8a-tetraazaanthracene-1(2H),5(6H)-dione (HTTA) is synthesized by chlorination previously reported 5,6-dihydro-1,3,5,5-tetramethylpyrazin-2(1H)-one with tert-butyl hypochlorite and self condensation resulting α-chloromethylimine in presence diisopropylethylamine dimethylformamide (DMF)....

Reaction of the verdazyl precursor 1,4,5,6-tetrahydro-2,4-dimethyl-6-(2′-pyridyl)-1,2,4,5-tetrazin-3(2H)-one (pvdH3) with oxygen and copper(I) bromide in acetonitrile results precipitation crystalline diradical di-μ-bromo-bis[(1,5-dimethyl-6-oxo-3-(2-pyridyl)verdazyl)copper(I)]. The solid shows a slightly anisotropic ESR spectrum magnetic susceptibility measurements indicate weak antiferromagnetic exchange between free radicals, consistent assignment as ion coordinated to radical.

The diradical methylenebis(1,5-diisopropyl-6-oxoverdazyl) was synthesized by benzoquinone oxidation of the corresponding bis(tetrazane). crystallizes in monoclinic space group C2/c with cell parameters a = 21.1411(8) A, b 12.4781(5) c 8.2457(3) beta 108.638(2) degrees, V 2061.15 A3, Z 4. Magnetic measurements indicate has singlet ground state and triplet excited at 150 cm(-1). Interaction between nonconjugated radical centers is also seen UV-vis spectrum as broad shoulder near 500 nm that...

Species that can undergo changes in electronic configuration as a result of an external stimulus such pH or solvent polarity play important role sensors, conducting polymers, and molecular switches. One way to achieve structures is couple two redox-active fragments, where the redox activity one them strongly dependent upon environment. We report on new verdazyls, subsituted with di-tert-butyl phenol group other dimethylaminophenyl group, have potential for behavior oxidation. Oxidation both...

Copper(I) forms mixed ligand coordination compounds with the stable, paramagnetic bipyridine analogue, 1,5-dimethyl-3-(2-pyridyl)-6-oxoverdazyl (pyvd) and a variety of monodentate bidentate phosphine ligands. These were characterized in solution by titration, UV-vis spectra, ESR spectra electrospray mass spectrometry. Coordination gives metal–ligand charge transfer transition that is red shifted more electron donating phosphines. indicates spin density on copper increases, both strongly...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis, structure, and reactivity of an antiaromatic, 2,5-dicarboxy-stabilized 1,4-dihydropyrazineDavid J. R. Brook, Curtis Haltiwanger, Tad H. KochCite this: Am. Chem. Soc. 1992, 114, 15, 6017–6023Publication Date (Print):July 1, 1992Publication History Published online1 May 2002Published inissue 1 July 1992https://pubs.acs.org/doi/10.1021/ja00041a018https://doi.org/10.1021/ja00041a018research-articleACS PublicationsRequest reuse...

Crystallization of the verdazyl-based valence tautomeric ion [Co(dipyvd)

Quantum entanglement between the spin states of a metal center and radical ligands is suggested in an iron(II) [Fe(dipyvd)2]2+ compound (dipyvd = 1-isopropyl-3,5-dipyridil-6-oxoverdazyl). Wave function ab initio (Difference Dedicated Configuration Interaction, DDCI) inspections were carried out to stress versatility local states. We named this phenomenon excited state spinmerism, reference our previous work (see Roseiro et al., ChemPhysChem2022, e202200478) where we introduced concept...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNew type of charge-transfer complex from an antiaromatic electron donor. Possible radical cation stabilization by the captodative effectDavid J. R. Brook, Curtis Haltiwanger, and Tad H. KochCite this: Am. Chem. Soc. 1991, 113, 15, 5910–5911Publication Date (Print):July 1, 1991Publication History Published online1 May 2002Published inissue 1 July 1991https://pubs.acs.org/doi/10.1021/ja00015a082https://doi.org/10.1021/ja00015a082research-articleACS...