@article{shultz_fico_bodnar_kumar_vostrikova_kampf_boyle_2003, title={Trends in exchange coupling for trimethylenemethane-type bis(semiquinone) biradicals and correlation of magnetic exchange with mixed valency for cross-conjugated systems}, volume={125}, ISSN={["0002-7863"]}, DOI={10.1021/ja0367849}, abstractNote={A magnetostructural correlation (conformational electron spin exchange modulation) within an isostructural series of biradical complexes is presented. X-ray crystal structures, variable-temperature electron paramagnetic resonance spectroscopy, zero-field splitting parameters, and variable-temperature magnetic susceptibility measurements were used to evaluate molecular conformation and electron spin exchange coupling in this series of molecules. Our combined results indicate that the ferromagnetic portion of the exchange couplings occurs via the cross-conjugated pi-systems, while the antiferromagnetic portion occurs through space and is equivalent to incipient bond formation. Thus, molecular conformation controls the relative amounts of ferro- and antiferromagnetic contributions to exchange coupling. In fact, the exchange parameter correlates with average semiquinone ring torsion angles via a Karplus-Conroy-type relation. Because of the natural connection between electron spin exchange coupling and electronic coupling related to electron transfer, we also correlate the exchange parameters in the biradical complexes to mixed valency in the corresponding quinone-semiquinone radical anions. Our results suggest that delocalization in the cross-conjugated, mixed-valent radical anions is proportional to the ferromagnetic contribution to the exchange coupling in the biradical oxidation states.}, number={38}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Shultz, DA and Fico, RM and Bodnar, SH and Kumar, RK and Vostrikova, KE and Kampf, JW and Boyle, PD}, year={2003}, month={Sep}, pages={11761–11771} }
 @article{shultz_vostrikova_bodnar_koo_whangbo_kirk_depperman_kampf_2003, title={Trends in metal-biradical exchange interaction for first-row M-II(nitronyl nitroxide-semiquinone) complexes}, volume={125}, ISSN={["0002-7863"]}, DOI={10.1021/ja020715x}, abstractNote={We report molecular structures and temperature-dependent magnetic susceptibility data for several new metal complexes of heterospin triplet ground-state biradical ligands. The ligands are comprised of both nitronyl-nitroxide (NN) and semiquinone (SQ) spin carriers. Five compounds are five-coordinate M(II) complexes (M = Mn, Co, Ni, Cu, and Zn), and one is a six-coordinate Ni(II) complex. Five compounds were structurally characterized. During copper complex formation a reaction with methanol occurs to form a unique methoxy-substituted SQ ring. Variable-temperature magnetic susceptibility studies are consistent with strong intraligand (NN-SQ and NN-PhSQ) ferromagnetic exchange coupling. For the five-coordinate Mn, Co, and Ni complexes, the S = 1 ligand is antiferromagnetically coupled to the metal. For both the five-coordinate Cu complex and the six-coordinate Ni complex, the ligand is ferromagnetically coupled to the metal spins in accordance with orbital symmetry arguments. Despite the low molecular symmetries, the predicted trend in metal-ligand exchange interactions is supported by spin dimer analysis based on extended Hückel calculations. For (NN-SQ)NiTp(Cum,Me)() (Tp(Cum,Me)() = hydro-tris(3-cumenyl-5-methylpyrazolyl)borate), an antisymmetric exchange term was required for the best fit of the magnetic susceptibility data. Antisymmetric exchange was less important for the other complexes due to inherently smaller Deltag. Finally, it is shown that intraligand exchange coupling is of paramount importance in stabilizing high-spin states of mixed metal-biradical complexes.}, number={6}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Shultz, DA and Vostrikova, KE and Bodnar, SH and Koo, HJ and Whangbo, MH and Kirk, ML and Depperman, EC and Kampf, JW}, year={2003}, month={Feb}, pages={1607–1617} }
 @article{caneschi_dei_mussari_shultz_sorace_vostrikova_2002, title={High-spin metal complexes containing a ferromagnetically coupled tris(semiquinone) ligand}, volume={41}, ISSN={["0020-1669"]}, DOI={10.1021/ic0106322}, abstractNote={The tris-bidentate ligand 1,3,5-tris(5'-tert-butyl-3',4'-dihydroxyphenyl)benzene ((TBCat)(3)Ph) was synthesized. The reaction of this molecule in basic solution with two paramagnetic acceptors, i.e., a nickel(II)minus signtetraazamacrocyclic ligand complex (Ni(CTH)) (CTH = dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) and manganese(II)-hydrotris[3-(4'-cumenyl)-5-methylpyrazolyl]borate (Mn(Tp(Cum,Me))), yielded two complexes whose analytical formulas are consistent with those of trinuclear complexes. Spectroscopic and magnetic measurements suggest that these derivatives contain divalent metal ions coordinated to the tris(semiquinone) form of the ligand. Analysis of the magnetic data shows that the pi-connectivity of the ligand enforces ferromagnetic coupling between the three semiquinone units of the molecule, giving rise to complexes with S = 9/2 (M = Ni(II)) and S = 6 (M = Mn(II)) ground states. The coupling within the tris(semiquinone) unit is quite large (J = -26 cm(-1) for the nickel(II) derivative and J = -40 cm(-1) for the manganese(II) one, using the general exchange Hamiltonian H = sigma J(ij)S(i)S(j)), and it is of the same order of magnitude as that observed in an analogous series of bis(semiquinone) complexes that we recently reported.}, number={5}, journal={INORGANIC CHEMISTRY}, author={Caneschi, A and Dei, A and Mussari, CP and Shultz, DA and Sorace, L and Vostrikova, KE}, year={2002}, month={Mar}, pages={1086–1092} }
 @article{depperman_bodnar_vostrikova_shultz_kirk_2001, title={Spin robustness of a new hybrid inorganic-organic high-spin molecule}, volume={123}, DOI={10.1021/ja003739h}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTSpin Robustness of a New Hybrid Inorganic−Organic High-Spin MoleculeEzra C. Depperman, Scot H. Bodnar, Kira E. Vostrikova, David A. Shultz, and Martin L. KirkView Author Information Department of Chemistry, The University of New Mexico Albuquerque, New Mexico 87131-1096 Department of Chemistry, North Carolina State University Raleigh, North Carolina 27695-8204 October 23, 2000Cite this: J. Am. Chem. Soc. 2001, 123, 13, 3133–3134Publication Date (Web):March 7, 2001Publication History Revised2 January 2001Published online7 March 2001Published inissue 1 April 2001https://doi.org/10.1021/ja003739hCopyright © 2001 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views214Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (33 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Electronic structure,Magnetic materials,Magnetic properties,Quantum mechanics,Spectroscopy Get e-Alerts}, number={13}, journal={Journal of the American Chemical Society}, author={Depperman, E. C. and Bodnar, S. H. and Vostrikova, K. E. and Shultz, David and Kirk, M. L.}, year={2001}, pages={3133–3134} }
 @article{shultz_bodnar_vostrikova_kampf_2000, title={Synthesis and structure of a complex having a quartet ground state with three entirely different spin carriers: Nitronyl nitroxide, o-semiquinone, and Cu-II}, volume={39}, ISSN={["0020-1669"]}, DOI={10.1021/ic0009122}, abstractNote={A "spin diverse" S = 3/2 ground-state complex, NN-SQCuTpCum,Me, has been prepared. The three S = 1/2 spin carriers are nitronyl nitroxide (NN), o-semiquinone (o-SQ), and cupric ion. The solid-state structure of the ZnII derivative, NN-SQZnTpCum,Me (C56H69BN8O4Zn), was determined: monoclinic, P2(1)/c, a = 12.5781(12) A, b = 17.7408(17) A, c = 24.440(2) A, alpha = 90.00 degrees, beta = 98.240(2) degrees, gamma = 90.00 degrees, Z = 4. The results of X-ray structural characterization of the ZnII derivative suggest substantial interaction between the two spin carriers NN and o-SQ. Indeed, strong intramolecular exchange coupling has been determined by variable-temperature magnetic susceptibility studies. Intraligand ferromagnetic exchange is considerably greater than kT, such that only the triplet state is populated at 300 K, and CuII-ligand exchange is ferromagnetic, with J = +75 cm-1.}, number={26}, journal={INORGANIC CHEMISTRY}, author={Shultz, DA and Bodnar, SH and Vostrikova, KE and Kampf, JW}, year={2000}, month={Dec}, pages={6091–6093} }