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1.
Chem Commun (Camb) ; 59(94): 13966-13969, 2023 Nov 23.
Artículo en Inglés | MEDLINE | ID: mdl-37933533

RESUMEN

Reaction of a trinuclear triangular macrocyclic complex Pb3L(CF3SO3)6 with bidentate linkers in a ratio of 3 equiv. of linker per 2 equiv. of complex, produces a prismatic structure with 4,4'-dipyridyl, and two unprecedented, extended 3D frustum-like structures with 1,2-di(4-pyridyl)ethylene and 1,4-di(4-pyridyl)benzene. The cavities of these structures encapsulate triflate anions.

2.
Dalton Trans ; 51(38): 14568-14580, 2022 Oct 04.
Artículo en Inglés | MEDLINE | ID: mdl-36074758

RESUMEN

Three [Cr6E8(PEt3)6] cluster molecules with E = S, Se, and Te have been synthesized by reaction of stoichiometric mixtures of Cr(II) and Cr(III) metal salts with silylated chalcogen reagents E(SiMe3)2 (E = S, Se, Te) in the presence of L = PEt3 = triethylphosphine. For the sulfide- and selenide-bridged clusters two crystallographic forms (trigonal R3̄ and triclinic P1̄), which differ in the presence of lattice solvent molecules, have been isolated. Structural data, optical spectra and quantum chemical calculations reveal the presence of low-lying excited states in [Cr6E8(PEt3)6] (E = S, Se), which would help in rationalizing the non-vanishing magnetic moments at 2 K revealed by DC magnetic measurements and EPR spectroscopy. These findings are partially in contrast to a previous report by Saito and co-workers (S. Kamiguchi, H. Imoto, T. Saito, Inorg. Chem., 1998, 37, 6852-6857.), who postulated an incorporated hydrogen atom as the source of paramagnetism at low temperatures for the trigonal forms of [Cr6E8(PEt3)6] (E = S, Se).

3.
Inorg Chem ; 61(1): 554-567, 2022 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-34931842

RESUMEN

7Li NMR shifts and magnetic properties have been determined for three so-called ate complexes [LiM{N(SiMe3)2}3] (M2+ = Mn, Fe, Co; e.g., named lithium-tris(bis(trimethylsilylamide))-manganate(II) in accordance with a formally negative charge assigned to the complex fragment [M{N(SiMe3)2}3]-, which comprises the transition metal). They are formed by addition reactions of LiN(SiMe3)2 and [M{N(SiMe3)2}2] and stabilized by Lewis base/Lewis acid interactions. The results are compared to those of the related "ion-separated" complexes [Li(15-crown-5)][M{N(SiMe3)2}3]. The ate complexes with the lithium atoms connected to the 3d metal atoms manganese, iron, or cobalt via µ2 nitrogen bridges reveal strong 7Li NMR paramagnetic shifts of about -75, 125, and 171 ppm, respectively, whereas the shifts for the lithium ions coordinated by the 15-crown-5 ether are close to zero. The observed trends of the 7Li NMR shifts are confirmed by density-functional theory calculations. The magnetic dc and ac properties display distinct differences for the six compounds under investigation. Both manganese compounds, [LiMn{N(SiMe3)2}3] and [Li(15-crown-5)][Mn{N(SiMe3)2}3], display almost pure and ideal spin-only paramagnetic behavior of a 3d5 high-spin complex. In this respect slightly unexpected, both complexes show slow relaxation behavior at low temperatures under applied dc fields, which is especially pronounced for the ate complex [LiMn{N(SiMe3)2}3]. Dc magnetic properties of the iron complexes reveal moderate g-factor anisotropies with small values of the axial magnetic anisotropy parameter D and a larger E (transversal anisotropy). Both complexes display at low temperatures and, under external dc fields of up to 5000 Oe, only weak ac signals with no maxima in the frequency range from 1 to 1500 s-1. In contrast, the two cobalt complexes display strong g-factor anisotropies with large values of D and E. In addition, in both cases, the ac measurements at low temperatures and applied dc fields reveal two, in terms of their frequency range, well separated relaxation processes with maxima lying for the most part outside of the measurement range between 1 and 1500 s-1.

4.
Inorg Chem ; 60(12): 8936-8945, 2021 Jun 21.
Artículo en Inglés | MEDLINE | ID: mdl-34110815

RESUMEN

The optical properties of four new trinuclear chalcogenolato bridged metal complexes [Ag2Ti(SPh)6(PPh3)2], [Na(thf)3]2[Ti(SPh)6], [Cu2Ti(SePh)6(PPh3)2], and [Ag2Ti(SePh)6(PPh3)2] have been investigated by absorption and photoluminescence spectroscopy as well as time-dependent density functional theory (TDDFT) calculations and compared to the results published recently for [Cu2Ti(SPh)6(PPh3)2]. All of these compounds are distinguished by efficient near-infrared luminescence at ∼880-1200 nm in the solid state at low temperatures, which remains quite intense for the copper-titanium complexes at ambient temperature with PL quantum yields of 9.5 and 4.8% at λPL = 1090 and 1240 nm for [Cu2Ti(EPh)6(PPh3)2], E = S, Se, respectively. According to the calculations, a peculiar feature of the lowest-energy electronic transitions in these complexes is their high localization on the metal and chalcogen atoms, with negligible contributions of the "external" ligand groups. Correspondingly, the type of atoms in the M2TiE6 (M = Cu, Ag, Na) core structure determines optical properties such as the absorption and emission wavelengths and PL lifetime.

5.
Dalton Trans ; 49(8): 2537-2546, 2020 Feb 25.
Artículo en Inglés | MEDLINE | ID: mdl-32022052

RESUMEN

We present the syntheses of trigonal planar coordinated Fe(ii) carbodiphosphorane (CDPR) complexes, starting from iron(ii)-bis(trimethylsilylamide) [Fe{N(SiMe3)2}2] and hexaphenyl-(CDPPh) and sym-dimethyltetraphenyl-carbodiphosphoranes (CDPMe), respectively. Both complexes [CDPPh-Fe{N(SiMe3)2}2] (1) and [CDPMe-Fe{N(SiMe3)2}2] (2) were examined in solution and in the solid state. 1 shows a dissociation equilibrium in solution which we monitored by variable temperature 1H-NMR spectroscopy. Magnetic measurements of 1 and 2 yielded a high spin configuration (S = 2) for both complexes. Quantum chemical calculations were performed to analyze the bonding situation in compound 1.

6.
Dalton Trans ; 48(41): 15699-15712, 2019 Oct 22.
Artículo en Inglés | MEDLINE | ID: mdl-31538172

RESUMEN

Systematic ac (alternating current) magnetic investigations on four new trigonal planar high-spin Fe2+ complexes [Fe{N(SiMe3)2}2L] reveal that complexes which comprise a phosphine or arsine type ligand (L = PPh3, PMe3 and AsPh3) display slow magnetic relaxation at temperatures below 8 K under applied dc (direct current) fields, whereas a complex with a phosphine oxide ligand (L = OPPh3) does not. Accordingly, the parameters characteristic for magnetic anisotropy, derived both from dc magnetic measurements and quantum chemical calculations, reveal distinct differences for these two types of complexes. Extensive ab initio calculations of multi-reference wave function type were performed on the four new complexes listed above and the related reported ones with L = py, thf and PCy3 in order to get a reasonable description of the local electronic states involved in the magnetic relaxation. These calculations confirm that strong spin-orbit effects generate the magnetic anisotropy of complexes with L = PPh3, PMe3, AsPh3 and PCy3. On the other hand, the complexes with L = OPPh3, py and THF exhibit only small spin-orbit splittings, consistent with the fast relaxation found experimentally.

7.
Dalton Trans ; 48(20): 6863-6871, 2019 May 21.
Artículo en Inglés | MEDLINE | ID: mdl-31021338

RESUMEN

The bidentate phosphine bis(diphenylphosphino)-N-phenyl-maleimide (L1) is used to synthesize a series of complexes from coinage metals and palladium. Some of them are mononuclear species where one metal atom is coordinated by two phosphine ligands. Three of these complexes have been investigated in detail because they contain the initial ligand in an anionic, radical form (L1') i.e. [Cu(L1L1')] (1), [Ag(L1L1')] (7), [Pd(L1')2] (11). L1' in 1, 7 and 11 shows significant differences in its bonding parameters compared to free or coordinating L1. By magnetic measurements the radical nature of these three compounds could be verified. Quantum chemical calculations prove the existence of either one (1 and 7) or two (11) unpaired electrons localized on the ligand. Furthermore these calculations can explain that 1 and 7 show an asymmetric structure in solid state where one can clearly differ L1 from L1'.

8.
Inorg Chem ; 57(2): 602-608, 2018 Jan 16.
Artículo en Inglés | MEDLINE | ID: mdl-29257688

RESUMEN

Reactions of [Mn{N(SiMe3)2}2]2 with 2.1 equiv of RSH, R = Ph or Mes = C6H2-2,4,6-(CH3)3, yield compounds of the formal composition "Mn(SR)2". Single-crystal X-ray diffraction reveals that ∞1[Mn(SMes)2] forms one-dimensional chains in the crystal via µ2-SMes bridges, whereas ∞3[Mn4(SPh)8] comprises a three-dimensional network in which adamantanoid cages composed of four Mn atoms and six µ2-bridging SPh ligands are connected in three dimensions by doubly bridging SPh ligands. Thermogravimetric analysis and powder diffractometry indicate an reversible uptake of solvent molecules (tetrahydrofuran) into the channels of ∞1[Mn(SMes)2]. Magnetic measurements reveal antiferromagnetic coupling for both compounds with J = -8.2 cm-1 (∞1[Mn(SMes)2]) and -10.0 cm-1 (∞3[Mn4(SPh)8]), respectively. Their optical absorption and photoluminescence (PL) excitation spectra display characteristic d-d bands of Mn2+ ions in the visible spectral region. Both compounds emit bright phosphorescence at ∼800 nm at low temperatures (<100 K). However, only ∞1[Mn(SMes)2] retains a moderately intense emission at ambient temperature (with a quantum yield of 1.2%). Similar PL properties are also found for the related selenolate complexes ∞1[Mn(SeR)2] (R = Ph, Mes).

9.
Angew Chem Int Ed Engl ; 56(43): 13253-13258, 2017 10 16.
Artículo en Inglés | MEDLINE | ID: mdl-28834005

RESUMEN

Reactions of [K(crypt-222)]2 (TlBi3 )⋅0.5 en (1 b) with [Ru(cod)(H2 CC(Me)CH2 )2 ] (A) in 1,2-diaminoethane (en) led to the formation of two compounds with new bismuth-rich cluster anions, [K(crypt-222)]3 [Bi9 {Ru(cod)}2 ]⋅1.5 en (2) and [K(crypt-222)]2 [Tl2 Bi6 {Ru(cod)}]⋅2 tol (3), alongside the salt of a binary nido cluster, [K(crypt-222)]3 (Tl4 Bi5 )⋅2 en (4). The anions in 2 and 3 are two further examples of rare heterometallic clusters containing Ru atoms. As one cod ligand is retained on each Ru atom in both clusters, the anions may be viewed as intermediates on the way towards larger, ligand-free intermetalloid clusters. Quantum-chemical studies provided insight into the bonding situation in these clusters. According to these studies, the anion of 2 features both electron-precise and electron-deficient parts. Electrospray ionization mass spectrometry analysis indicated that the clusters undergo stepwise fragmentation.

10.
Inorg Chem ; 56(15): 9330-9336, 2017 Aug 07.
Artículo en Inglés | MEDLINE | ID: mdl-28731683

RESUMEN

A homologous series of three copper-tin-chalcogenide cluster molecules [Cu6E6(SnPh)2(PPh2Et)6] (E = S, Se, Te) was synthesized by reactions of CuO(O)CCH3 and PhSnCl3 with E(SiMe3)2 in the presence of PPh2Et. The cluster cage structures are similar, with slight differences in the bridging modes of the respective chalcogenide ligands E. The onset of the optical absorption displays a significant decrease of ca. 1.1 eV on going from sulfur to tellurium. The differences in bonding and electronic excitations can be rationalized by DFT and TDDFT calculations. All complexes display near-infrared phosphorescence at cryogenic temperatures. In parallel with the absorption, the emission maximum shifts to lower energies in a series of sulfur, selenium, and tellurium compounds. In particular, the copper-tin-tellurium complex emits at an energy as low as ca. 0.97 eV (1280 nm).

11.
Dalton Trans ; 46(5): 1502-1509, 2017 Jan 31.
Artículo en Inglés | MEDLINE | ID: mdl-28091649

RESUMEN

The optical properties of four isostructural trinuclear chalcogenolato bridged metal complexes [Cu2Sn(SPh)6(PPh3)2], [Cu2Sn(SePh)6(PPh3)2], [Ag2Sn(SPh)6(PPh3)2] and [Cu2Ti(SPh)6(PPh3)2] have been investigated by absorption and photoluminescence spectroscopy and time-dependent density functional theory (TDDFT) calculations. All copper-tin compounds demonstrate near-infrared (NIR) phosphorescence at ∼900-1100 nm in the solid state at low temperature, which is nearly absent at ambient temperature. Stokes shifts of these emissions are found to be unusually large with values of about 1.5 eV. The copper-titanium complex [Cu2Ti(SPh)6(PPh3)2] also shows luminescence in the NIR at 1090 nm but with a much faster decay (τ ∼ 10 ns at 150 K) and a much smaller Stokes shift (ca. 0.3 eV). Even at 295 K this fluorescence is found to comprise a quantum yield as high as 9.5%. The experimental electronic absorption spectra well correspond to the spectra simulated from the calculated singlet transitions. In line with the large Stokes shifts of the emission spectra the calculations reveal for the copper-tin complexes strong structural relaxation of the excited triplet states whereas those effects are found to be much smaller in the case of the copper-titanium complex.

12.
Dalton Trans ; 45(43): 17382-17391, 2016 Nov 01.
Artículo en Inglés | MEDLINE | ID: mdl-27722702

RESUMEN

Reactions of [Co(N(SiMe3)2)2thf] with 2.1 equiv. of MesSH (Mes = C6H2-2,4,6-(CH3)3) yield dark brown crystals of the one dimensional chain compound [Co(SMes)2]. In contrast reactions of [Co(N(SiMe3)2)2thf] with 2.1 equiv. of PhSH result in the formation of a dark brown almost X-ray amorphous powder of 'Co(SPh)2'. Addition of aliquots of CH3OH to the latter reaction resulted in the almost quantitative formation of crystalline ammonia thiolato complexes either [Co(SPh)2(NH3)2] or [Co(SPh)2NH3]. Single crystal XRD reveals that [Co(SPh)2NH3] forms one-dimensional chains in the crystal via µ2-SPh bridges whereas [Co(SPh)2(NH3)2] consists at a first glance of isolated distorted tetrahedral units. Magnetic measurements suggest strong antiferromagnetic coupling for the two chain compounds [Co(SMes)2] (J = -38.6 cm-1) and [Co(SPh)2NH3] (J = -27.1 cm-1). Interestingly, also the temperature dependence of the susceptibility of tetrahedral [Co(SPh)2(NH3)2] shows an antiferromagnetic transition at around 6 K. UV-Vis-NIR spectra display d-d bands in the NIR region between 500 and 2250 nm. Thermal gravimetric analysis of [Co(SPh)2(NH3)2] and [Co(SPh)2NH3] reveals two well separated cleavage processes for NH3 and SPh2 upon heating accompanied by the stepwise formation of 'Co(SPh)2' and cobalt sulfide.

13.
Inorg Chem ; 55(5): 2091-100, 2016 Mar 07.
Artículo en Inglés | MEDLINE | ID: mdl-26900764

RESUMEN

Direct current (dc) and alternating current (ac) magnetic measurements have been performed on the three Ni(I) complexes: [NiCl(PPh3)3], [NiCl(PPh3)2]·C4H8O, and [Ni(N(SiMe3)2)(PPh3)2]. Fits of the dc magnetic data suggest an almost similar behavior of the three compounds, which display only moderate deviations from the spin-only values. The ac magnetic investigations reveal that the two complexes with trigonal planar coordination--[NiCl(PPh3)2]·C4H8O and [Ni(N(SiMe3)2)(PPh3)2]--display slow magnetic relaxation at low temperatures under applied dc fields, whereas tetrahedral [NiCl(PPh3)3] does not. Ground and excited states as well as magnetic data were calculated by ab initio wave function based multi-configurational methods, including dynamic correlation as well as spin-orbit coupling. The two trigonal planar complexes comprise well-isolated S = (1)/2 ground states, whereas two S = (1)/2 states with a splitting of less than 100 cm(-1) were found in the tetrahedral compound.

14.
Angew Chem Int Ed Engl ; 54(48): 14345-8, 2015 Nov 23.
Artículo en Inglés | MEDLINE | ID: mdl-26449964

RESUMEN

The thermal and photochemical E/Z isomerization of camphorquinone-derived imines was studied by a combination of kinetic, structural, and computational methods. The thermal isomerization proceeds by linear N inversion, whereas the photoinduced process occurs through C=N bond rotation with preferred directionality as a result of diastereoisomerism. Thereby, these imines are arguably the simplest example of synthetic molecular motors. The generality of the orthogonal trajectories of the thermal and photochemical pathways allows for the postulation that every suitable chiral imine qualifies, in principle, as a molecular motor driven by light or heat.

15.
Inorg Chem ; 54(19): 9413-22, 2015 Oct 05.
Artículo en Inglés | MEDLINE | ID: mdl-26378617

RESUMEN

The electronic properties of a series of eight copper chalcogenide clusters including [Cu12S6(dpppt)4] (dpppt = Ph2P(CH2)5PPh2), [Cu12Se6(dppo)4] (dppo = Ph2P(CH2)8PPh2), [Cu12S6(dppf)4] (dppf = Ph2PCpFeCpPPh2), [Cu12S6(PPh2Et)8], [Cu12S6(PEt3)8], [Cu24S12(PEt2Ph)12], [Cu20S10(PPh3)8], and [Cu20S10(P(t)Bu3)8] were investigated by absorption and photoluminescence (PL) spectroscopy as well as time-dependent density functional theory calculations. Major features of the experimental electronic absorption spectra are generally well-reproduced by the spectra simulated from the calculated singlet transitions. Visualization of the nonrelaxed difference densities indicates that for all compounds transitions at higher energies (above ∼2.5 eV, i.e., below ∼495 nm) predominantly involve excitations of electrons from orbitals of the cluster core to ligand orbitals. Conversely, the natures of the lower-energy transitions are found to be highly sensitive to the specifics of the ligand surface. Bright red PL (centered at ∼650-700 nm) in the solid state at ambient temperature is found for complexes with all 'Cu12S6' (E = S, Se) cores as well as the dimeric 'Cu24S12', although in [Cu12S6(dppf)4], the PL appears to be efficiently quenched by the ferrocenyl groups. Of the two isomeric 'Cu20S10' complexes the prolate cluster [Cu20S10(PPh3)8] shows a broad emission that is centered at ∼820 nm, whereas the oblate cluster [Cu20S10(P(t)Bu3)8] displays a relatively weak orange emission at ∼575 nm. The emission of all complexes decays on the time scale of a few microseconds at ambient temperature. A very high photostability is quantitatively estimated for the representative complex [Cu12S6(dpppt)4] under anaerobic conditions.

16.
Chem Commun (Camb) ; 50(75): 11043-5, 2014 Sep 28.
Artículo en Inglés | MEDLINE | ID: mdl-25098944

RESUMEN

The synthesis, molecular structures and luminescence properties of two 'Cu12S6' cluster molecules with stabilizing bidentate phosphine ligands are described. Both display in the solid state at ambient temperature high photoluminescence quantum yields (≥48%) and good stability towards oxygen.

17.
Inorg Chem ; 53(4): 1962-74, 2014 Feb 17.
Artículo en Inglés | MEDLINE | ID: mdl-24467294

RESUMEN

Alternating current magnetic investigations on the trigonal-planar high-spin Co(2+) complexes [Li(15-crown-5)] [Co{N(SiMe3)2}3], [Co{N(SiMe3)2}2(THF)] (THF = tetrahydrofuran), and [Co{N(SiMe3)2}2(PCy3)] (Cy = -C6H13 = cyclohexyl) reveal that all three complexes display slow magnetic relaxation at temperatures below 8 K under applied dc (direct current) fields. The parameters characteristic for their respective relaxation processes such as effective energy barriers Ueff (16.1(2), 17.1(3), and 19.1(7) cm(-1)) and relaxation times τ0 (3.5(3) × 10(-7), 9.3(8) × 10(-8), and 3.0(8) × 10(-7) s) are almost the same, despite distinct differences in the ligand properties. In contrast, the isostructural high-spin Fe(2+) complexes [Li(15-crown-5)] [Fe{N(SiMe3)2}3] and [Fe{N(SiMe3)2}2(THF)] do not show slow relaxation of the magnetization under similar conditions, whereas the phosphine complex [Fe{N(SiMe3)2}2(PCy3)] does, as recently reported by Lin et al. (Lin, P.-H.; Smythe, N. C.; Gorelsky, S. I.; Maguire, S.; Henson, N. J.; Korobkov, I.; Scott, B. L.; Gordon, J. C.; Baker, R. T.; Murugesu, M. J. Am. Chem. Soc. 2011, 135, 15806.) Distinctly differing axial anisotropy D parameters were obtained from fits of the dc magnetic data for both sets of complexes. According to density functional theory (DFT) calculations, all complexes possess spatially nondegenerate ground states. Thus distinct spin-orbit coupling effects, as a main source of magnetic anisotropy, can only be generated by mixing with excited states. This is in line with significant contributions of excited determinants for some of the compounds in complete active space self-consistent field (CASSCF) calculations done for model complexes. Furthermore, the calculated energetic sequence of d orbitals for the cobalt compounds as well as for [Fe{N(SiMe3)2}2(PCy3)] differs significantly from the prediction by crystal field theory. Experimental and calculated (time-dependent DFT) optical spectra display characteristic d-d transitions in the visible to near-infrared region. Energies for lowest transitions range from 0.19 to 0.35 eV; whereas, for [Li(15-crown-5)][Fe{N(SiMe3)2}3] a higher value is found (0.66 eV). Zero-field (57)Fe Mößbauer spectra of the three high-spin iron complexes exhibit a doublet at 3 K with small and similar values of the isomer shifts (δ), ranging between 0.57 and 0.59 mm/s, as well as an unusual small quadrupole splitting (ΔEQ = 0.60 mm/s) in [Li(15-crown-5)][Fe{N(SiMe3)2}3].

18.
Chemistry ; 19(6): 1986-95, 2013 Feb 04.
Artículo en Inglés | MEDLINE | ID: mdl-23280759

RESUMEN

Treatment of N,N'-bis(4carboxysalicylidene)ethylenediamine (H(4)L), with MnCl(2)⋅(H(2)O)(4), and Ln(NO(3))(3)⋅(H(2)O)(m) (Ln = Nd, Eu, Gd, Dy, Tb), in the presence of N,N-dimethylformamide (DMF)/pyridine at elevated temperature resulted (after work up) in the formation of 1D coordination polymers {[Ln(2)(MnLCl)(2)(NO(3))(2)(dmf)(5)]⋅4 DMF}(n) (1-5). In these coordination polymers the rare earth ions are connected through carboxylate groups from Mn-salen units in a 1D chain structure. Thus, the Mn-salen complex acts as a "metalloligand" with open coordination sites. All compounds were used as catalysts in the liquid-phase epoxidation of trans-stilbene with molecular oxygen, which resulted in the formation of stilbene oxide. Since the choice of the lanthanide had virtually no influence on the performance of the catalyst, only the manganese-gadolinium was studied in detail. The influence of solvent, catalyst concentration, reaction temperature, oxidant, and oxidant flow rate on conversion, yield, and selectivity was analyzed. A conversion of up to 70%, the formation of 61% stilbene oxide (88% selectivity), and a TON of 84 were observed after 24 h. A hot filtration test confirmed that the reaction is mainly catalyzed through a heterogeneous pathway, although a minor contribution of homogeneous species could not be completely excluded. The catalyst could be reused without significant loss of activity.

19.
Photochem Photobiol Sci ; 11(6): 1069-80, 2012 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-22522667

RESUMEN

Semisynthetic zinc chlorins are shown for the first time to self-assemble in the absence of an intrinsic hydroxy group, which is always present in the chlorosomal bacteriochlorophylls (BChl's) c, d and e. Instead, the presently studied compounds have carbonyl groups. These cannot function as hydrogen bond donating groups. However due to interspacing water molecules bound to the zinc ion, double hydrogen bonding can occur to adjacent tetrapyrrolic macrocycles equipped with carbonyl recognition groups. Solution studies comprising UV-Vis absorption, electronic circular dichroism (ECD) and FT-IR show that different aggregates are formed in hydrated solvents in comparison to dry nonpolar solvents. Single crystal X-ray studies show variable supramolecular interactions either with interspacing water molecules coordinating the Zn ion within a porphyrin or with the 17(2) carbonyl group of a chlorin ligating the Zn ion. Our findings have implications for a minimalistic design of self-assembling chromophores, which can act as efficient light-harvesting units.


Asunto(s)
Metaloporfirinas/química , Porfirinas/química , Agua/química , Bacterioclorofilas/química , Bacterioclorofilas/metabolismo , Materiales Biomiméticos/química , Materiales Biomiméticos/metabolismo , Cristalografía por Rayos X , Enlace de Hidrógeno , Metaloporfirinas/síntesis química , Conformación Molecular
20.
Inorg Chem ; 51(5): 2747-56, 2012 Mar 05.
Artículo en Inglés | MEDLINE | ID: mdl-22356421

RESUMEN

The ternary clusters (tmeda)(6)Zn(14-x)Mn(x)S(13)Cl(2) (1a-d) and (tmeda)(6)Zn(14-x)Mn(x)Se(13)Cl(2) (2a-d), (tmeda = N,N,N',N'-tetramethylethylenediamine; x ≈ 2-8) and the binary clusters (tmeda)(6)Zn(14)E(13)Cl(2) (E = S, 3; Se, 4;) have been isolated by reacting (tmeda)Zn(ESiMe(3))(2) with Mn(II) and Zn(II) salts. Single crystal X-ray analysis of the complexes confirms the presence of the six "(tmeda)ZnE(2)" units as capping ligands that stabilize the clusters, and distorted tetrahedral geometry around the metal centers. Mn(II) is incorporated into the ZnE framework by substitution of Zn(II) ions in the cluster. The polynuclear complexes (tmeda)(6)Zn(12.3)Mn(1.7)S(13)Cl(2)1a, (tmeda)(6)Zn(12.0)Mn(2.0)Se(13)Cl(2)2a, and (tmeda)(6)Zn(8.4)Mn(5.6)Se(13)Cl(2)2d represent the first examples of "Mn/ZnE" clusters with structural characterization and indications of the local chemical environment of the Mn(II) ions. The incorporation of higher amounts of Mn into 1d and 2d has been confirmed by elemental analysis. Density functional theory (DFT) calculations indicate that replacement of Zn with Mn is perfectly feasible and at least partly allows for the identification of some sites preferred by the Mn(II) metals. These calculations, combined with luminescence studies, suggest a distribution of the Mn(II) in the clusters. The room temperature emission spectra of clusters 1c-d display a significant red shift relative to the all zinc cluster 3, with a peak maximum centered at 730 nm. Clusters 2c-d display a peak maximum at 640 nm in their emission spectra.

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