bluuebunny/crossref_metadata_2025_split huggingface dataset:
2,3‐Dihydrospiro[1H‐4‐ and 5‐azabenzimidazole‐2,1′ ‐cyclohexane] ( = Spiro[cyclohexane‐1,2′(3′H)‐1′H‐imidazo[4,5‐b]pyridine] and Spiro[cyclohexane‐1,2′(3′H)‐1′H‐imidazo[4, 5‐c]pyridine]): Reactions with Nucleophiles
Authors: Schwoch Stefan , Kramer Walter , Neidlein Richard , Suschitzky Hans 
Published: December 2004

AbstractThe readily available title compounds 4a and 24 react with N‐, O‐, S‐, and C‐nucleophiles in presence of MnO2 to give the corresponding mono‐ or disubstituted 2H‐azabenzimidazoles ( = azaisobenzimidazoles), e.g., 11–18 and 26a–h, respectively, or 2,3‐dihydro‐1H‐azabenzimidazoles ( = dihydro‐azabenzimidazoles) such as 9 and 10 and 27 and 28, respectively, by a 1, 4‐ or 1,6‐Michael addition (Schemes 2 and 4). The bromo‐dihydro‐1H‐azabenzimidazole 4b lost the Br‐atom when treated with piperidine or morpholine yielding the corresponding disubstituted 2H‐azabenzimidazole 21 (Scheme 3). Reductive ring opening of the substituted spiro compounds leads to mono‐ and disubstituted diaminopyridines which are intermediates for fused pyridine ring systems with substituents often not available by conventional routes and of potential pharmaceutical interest (see 32–37). E.g., starting from 4a, a three‐step synthesis of the analgesic flupirtine maleate (= ethyl {2‐amino‐6‐[(4‐fluorobenzyl)amino]pyridin‐3‐yl}carbamate maleate = Katadolon®; 39) and of its non‐fluorinated derivative D‐7195 is described. Its analogue 40 was similarly made from the spiro compound 24.
Gas‐Phase Generation and Characterization of Nitrileimine, HCNNH: A new, stable isomer of diazomethane
Authors: Goldberg Norman , Fiedler Andreas , Schwarz Helmut 
Published: December 2004

AbstractA new isomer of diazomethane 1, the nitrile imine, HCNNH (2) is reported to be a stable molecule in the gas phase. Upon neutralizing the α‐distonic HCNNH+ cation in a beam experiment, this long‐time predicted ylide can be generated. The experiments are supported by theoretical calculations (DFT/HF hybride method) on the neutral and cationic diazomethane 1, nitrile imine 2, and N‐isocyano amine 3 as well as the transition states for their interconversion.
Tetraethynylethenes: Fully cross‐conjugated π‐electron chromophores and molecular scaffolds for all‐carbon networks and carbon‐rich nanomaterials
Authors: Anthony John , Boldi Armen M. , Rubin Yves , Hobi Markus , Gramlich Volker , Knobler Carolyn B. , Seiler Paul , Diederich François 
Published: December 2004

AbstractThe preparation of tetraethynylethene (3,4‐diethynylhex‐3‐ene‐1,5‐diyne) 1 as well as of a great diversity of differentially mono‐, di‐, and triprotected derivatives by newly developed synthetic routes is described. These fully cross‐conjugated molecules are versatile building blocks and precursors to two‐dimensional all‐C networks and novel C‐rich nanoarchitecture with unusual structural and electronic properties, such as perethynylated expanded radialenes, or molecular wires and polymers with the novel polytriacetylene backbone. A key step in all of these routes was the Corey‐Fuchs dibromoolefination of aldehydes and ketones. Dibromoolefination of silyl‐protected penta‐1,4‐diyn‐3‐ones yielded the corresponding dibromomethylidene derivatives which, by twofold Pd‐catalyzed alkyne coupling, were transformed into tetraethynylethene derivatives. In routes to tetraethynylethenes with free cis‐or trans‐enediyne moieties, dibromoolefination of aldehyde groups produced geminal dibromoethenes which, upon elimination/metallation with LDA followed by quenching with H+ or other electrophiles, yielded free or substituted ethynyl groups in high yields. Tetra‐ and triprotected tetraethynylethenes are rather stable compounds that could be isolated in pure form, whereas derivatives with two or more free CH termini were only stable in dilute solution and polymerized rapidly in pure form. A trans‐bis(triisopropylsilyl)‐protected derivative represented an exception and could be isolated as stable crystals. X‐Ray analysis revealed that the two bulky (i‐Pr)3Si groups isolate the reactive chromophores from one another in the crystal and prevent intermolecular reactions. The structures of several tetraethynylethenes were revealed in high‐quality X‐ray crystal structures.
Salmycin A–D, Antibiotika aus Streptomyces violaceus, DSM 8286, mit Siderophor‐Aminoglycosid‐Struktur
Authors: Vértesy László , Aretz Werner , Fehlhaber Hans‐Wolfram , Kogler Herbert 
Published: December 2004

Salmycin A–D, Antibiotics from Strep tomy ces violaceus, DSM 8286, Having a Siderophor‐Aminoglycoside StructureSalmycin B (2) and C (3) were isolated under acid conditions, under which they are stable, from the culture broth of Streptomyces violaceus, DSM 8286. The acid‐ and alkaline‐labile, native main component salmycin A (1), as well as salmycin D (4), were obtained under strictly neutral pH conditions. The compounds 1 (C41H70FeN7O21), 2 (C41H69FeN6O21), 3 (C40H67FeN6O21), and 4 (C40H68FeN7O21) are classified as sideromycins and are stable when dry. Mild alkaline hydrolysis of 1 and 2 yielded the known siderophor danoxamin (5; C27H46FeN5O11), and amino‐disaccharides. The amino‐glycoside 6 (C14H25NO11) of salmycin B was stabilized by hydrogenation and the structure of the corresponding peracetate 10 determined by 1H,1H‐ and 1H,13C‐correlation NMR spectroscopy (Table 1). Compound 6 consists of a glucos‐2‐ulose unit which is linked to the 2‐position of a 6‐deoxy‐6‐(methylamino)heptopyranose. The danoxamin is bonded via the carboxy group by ester linkage to the primary alcohol of the glucos‐2‐ulose. Salmycin A (1) is a natural oxime of 2, it was synthesized from 2 with hydroxylamine. The salmycins and those derivatives which contain hexapyranos‐2‐ulose form stable ketone hydrates which can be identified by mass spectrometry. Although several recently identified features of the danomycins do not correspond with those of the salmycins, 13C‐NMR spectra show that both groups of antibiotics are closely related. All salmycins, especially component 1, are highly active against Staphylococci and Streptococci, even against resistant strains of these pathogens.
Microscopic Protonation/Deprotonation Equilibria of the Anti‐Inflammatory Agent Piroxicam
Authors: Takács‐Novák Krisztina , Kökösi József , Podányi Benjámin , Noszál Béla , Tsai Ruey‐Shiuan , Lisa Giuseppe , Carrupt Pierre‐Alain , Testa Bernard 
Published: December 2004

AbstractThe microscopic ionization behavior of piroxicam was investigated using two different approaches, i.e., direct UV spectroscopy and an indirect analogue approach (deductive method). The best microscopic pKa values (pKa12 = 4.60, pKa21 = 5.40, pKa22 = 2.72, and pKa11 = 1.92) were obtained by the deductive method using as pKa22 the pKa of the enolic O‐methylated piroxicam 2. The results show remarkable electrostatic effects in the protonation/deprotonation equilibria, a marked increase in the acidity of the enolic function (2.68 pKa units) being caused by the pyridinium group. The electronic structure of piroxicam was studied based on 1H‐NMR chemical shifts at various ionization states, indicating an extended electron conjugation through the molecule. The partition measurements in octan‐1‐ol/H2O of zwitterionic compound 3 (the pyridyl N‐methyl derivative of piroxicam (1)) suggest that the two opposite charges in zwitterionic piroxicam are indeed in a close intramolecular proximity.
L‐Phenylalanine Cyclohexylamide: A simple and convenient auxiliary for the synthesis of optically pure α,α‐disubstituted (R)‐ and (S)‐amino acids
Authors: Obrecht Daniel , Bohdal Udo , Broger Clemens , Bur Daniel , Lehmann Christian , Ruffieux Ruth , Schönholzer Peter , Spiegler Clive , Müller Klaus 
Published: December 2004

AbstractThis work describes L‐phenylalanine cyclohexylamide (5c) as a simple, cheap, and powerful chiral auxiliary for the synthesis of a series of optically pure α,α‐disubstituted (R)‐ and (S)‐amino acids of type 1, such as (R)‐ and (S)‐2‐methyl‐phenylalanine (1a), (R)‐ and (S)‐2‐methyl‐2‐phenylglycine (1b), and (R)‐ and (S)‐2‐methylvaline (1c; Scheme 3). These amino acids were efficiently transformed into the suitably protected and activated amino acid building blocks (R)‐ and (S)‐12b and (R)‐ and (S)‐12c (Scheme 4) which are ready for incorporation into peptides by solution or solid‐phase techniques. Based on the crystal structures of 6b, 6c, and 7a belonging to the diastereoisomeric peptides series 6 and 7, the absolute configurations of each member of the series were determined. β‐Turn geometries of type II′ and I were observed for 6b and 7a, respectively, whereas 6c crystallized in an extended conformation. The impacts of side‐chain variation on conformation and crystal packing of these triamides are discussed.
Synthesis of the Dolabellane Diterpene Hydrocarbon (±)‐δ‐araneosene
Authors: Jenny Luzi , Borschberg Hans‐Jürg 
Published: December 2004

AbstractThe racemic form of the bicyclic diterpene hydrocarbon δ‐araneosene (4), endowed with the dolabellane skeleton, was prepared from geraniol in two different ways. The more efficient route involved 13 steps and proceeded with an overall yield of 3.6% (average: 77% per step). With this reference sample at hand, the hitherto elusive metabolite (−)‐4, a likely biogenetic precursor of cycloaraneosene ((−)‐3) and sordaricin ((−)‐1), could finally be isolated in ≥ 99.5% purity from the neutral fractions of the mold Sordaria araneosa CAIN (Ascomycetes).
Oligodeoxyribonucleotides Containing 4‐Aminobenzimidazole in Place of Adenine: Solid‐phase synthesis and base pairing
Authors: Seela Frank , Wenzel Thomas 
Published: December 2004

AbstractOligonucleotides containing 4‐aminobenzimidazole 2′‐deoxyribofuranoside (1,3‐dideaza‐2′‐deoxyadenosine; c1c3Ad, 1) were synthesized. For this purpose, various NH2‐protecting groups were investigated, and the [(9H‐fluoren‐9‐yl)methoxy]carbonyl group was selected for phosphoramidite protection (→ 4c). Apart from the phosphoramidite 3, the phosphonate 2 was prepared. Compound 1 was incorporated in a homooligonuclectide as well as in oligomers containing naturally occurring nucleosides. The Tm values and the thermodynamic data of various duplexes (11 · 10, 17 · 10, 18 · 10) containing 4‐aminobenzimidazole were determined. Although d[(c1c3A)20] (11) does not form a Hoogsteen duplex with d(T20) (10) as observed with d[(c1A)20], it destabilizes the Watson‐Crick duplexes to a much smaller extent than it was expected from a bulged loop structure. Apparently, 4‐aminobenz‐imidazole interacts with regular nucleoside residues within a Watson‐Crick duplex structure, most likely by vertical stacking. According to the low basicity of the amino group, only weak H‐bonding is expected.
Unexpected Hydroxyspirolactone Formation upon Baeyer‐Villiger Oxidation of a trans‐α‐decalone (trans‐octahydronaphthalen‐1(2H)‐one) and X‐ray structure of the product
Authors: Demnitz F. W. Joachim , Freiberger Sabine , Weber Hans‐Peter 
Published: December 2004

Abstracttrans‐4,4,10‐Trimethyl‐9‐decalone ( = trans‐5,5,8a‐trimethyl‐octahydronaphthalen‐1(2H)‐one; 1), when treated with trifluoroperacetic acid, gave the unexpected hydroxyspirolactone 7‐hydroxy‐7,11,11‐trimethyl‐1‐oxaspiro[5.5]undecan‐2‐one (6), in which the two new O‐atoms were introduced in a 1,2‐trans relationship. The structure of this compound was conclusively proven by X‐ray crystallography. The process involves the intermediacy of 7‐membered lactone 2, the expected Baeyer‐Villiger product, which could also be successfully prepared under controlled conditions at 0° in a buffered medium containing Na2HPO4.
Absolute Rate Constants for the Addition of Benzyl (PhĊH2) and Cumyl (PhĊMe2) Radicals to Alkenes in Solution
Authors: Walbiner Manfred , Wu Jie Qiang , Fischer Hanns 
Published: December 2004

AbstractAbsolute rate constants and their temperature dependence were determined by time‐resolved electron spin resonance for the addition of the radicals PhĊH2 and PhĊMe2 to a variety of alkenes in toluene solution. To vinyl monomers CH2=CXY, PhĊH2 adds at the unsubstituted C‐atom with rate constants ranging from 14 M−1S−1 (ethoxyethene) to 6.7 · 103 M−1S−1 (4‐vinylpyridine) at 296 K, and the frequency factors are in the narrow range of log (A/M−1S−1) = 8.6 ± 0.3, whereas the activation energy varies with the substituents from ca. 51 kJ/mol to ca. 26 kJ/mol. The rate constants and the activation energies increase both with increasing exothermicity of the reaction and with increasing electron affinity of the alkenes and are mainly controlled by the reaction enthalpy, but are markedly influenced also by nucleophilic polar effects for electron‐deficient substrates. For 1,2‐disubstituted and trisubstituted alkenes, the rate constants are affected by additional steric substituent effects. To acrylate and styrenes, PhĊMe2 adds with rate constants similar to those of PhĊH2, and the reactivity is controlled by the same factors. A comparison with relative‐rate data shows that reaction enthalpy and polar effects also dominate the copolymerization behavior of the styrene propagation radical.
7‐Substituted 7‐Deaza‐2′‐deoxyguanosines: Regioselective Halogenation of Pyrrolo[2,3‐d]pyrimidine Nucleosides
Authors: Ramzaeva Natalya , Seela Frank 
Published: December 2004

AbstractThe synthesis of 7‐chloro‐, 7‐bromo‐, and 7‐iodo‐substituted 7‐deaza‐2′‐deoxyguanosine derivatives 2b–d is described. The regioselective 7‐halogenation with N‐halogenosuccinimides was accomplished using 7‐[2‐deoxy‐3,5‐O‐di(2‐methylpropanoyl)‐β‐D‐erythro‐ pentofuranosyl]‐2‐(formylamino)‐4‐methoxy‐7H‐pyrrolo[2,3‐d]‐ pyrimidine (4) as the common precursor. A one‐pot reaction (2N aq. NaOH) of the halogenated intermediates 5a–c furnished the desired compounds. Also the 7‐hexynyl derivative 2e of 7‐deaza‐2′‐deoxyguanosine is described.
Synthetic Attempts towards Polymers with Pentafulvene Structural Units
Authors: Zhang Gengyi , Neuenschwander Markus 
Published: December 2004

AbstractSynthetic attempts towards fully conjugated polymers 9 with pentafulvene‐diyl structural units are described. Cationic polymerization of pentafulvenes 1a (R = X = Me) and 1b (R = X = MeS) nearly quantitatively gives polymers 8a and 8b with typical Mn and Mw values of 38800 and 53750, respectively, for 8a, and 12000 and 35900, respectively, for 8b. Key step of the conversion 8a → 9a (Scheme 6) is a quantitative bromination 8a → 32a, the structure of 32a being confirmed by analytical data as well as by spectroscopic comparison with model compound 23. Best results in view of two‐fold the HBr elimination 32a → 9a are obtained with Et3N, but so far elimination has not been complete. Synthetic sequences are optimized with model compound 21 (Scheme 4). Here again, bromination 21 → 23 is quantitative, while two‐fold HBr elimination 23 → 22 with Et3N proceeds in 51% yield. Dibromide 23 easily undergoes HBr elimination followed by a Br shift to give bromide 29. Contrary to cationic polymerization, anionic polymerization of simple pentafulvenes 1 to 2 (which would be attractive in view of the conjugated polymers 3) is not successful: For pentafulvene 1b (R = X = MeS), the main reaction is Diels‐Alder‐type dimerization 1b → 15b (Scheme 2), even under anionic conditions.
Oligosaccharide Analogues of Polysaccharides. Part 4. Synthesis of a monosaccharide‐derived octamer
Authors: Alzeer Jawad , Vasella Andrea 
Published: December 2004

AbstractNaSMe in toluene leads to regioselective de‐C‐silylation of the bis[(trimethylsilyl)ethynyl]saccharide 2, but to decomposition of butadiynes such as 1 or 12. We have, therefore, combined the known reagent‐controlled, regioselective desilylation of 2 and of 12 (AgNO2/KCN) with a substrate‐controlled regioselective de‐C‐silylation, based on C‐silyl groups of different size. This combination was studied with the fully protected 3 which was mono‐desilylated to 4 or to 5 (Scheme 1). Triethylsilylation of 5 (→ 6) was followed by removal of the Me3Si group (→ 7), introduction of a (t‐Bu)Me2Si group (→ 8) and removal of the Et3Si group yielded 9; these high‐yielding transformations proceed with a high degree of selectivity. Iodination of 4 gave 10. The latter was coupled with 5 to the homodimer 11 and the heterodimer 12, which was desilylated to 13. The second building block for the tetramer was obtained by coupling 14 (from 7) with 5, leading to 15 and 16. Removal of the Me3Si group (→ 17) and iodination led to 18 which was coupled with 13 to the homotetramer 20 and the heterotetramer 19 (Scheme 2). Deprotection of 19 gave 21, which was, on the one hand, iodinated to 22, and, on the other hand, protected by the (t‐Bu)Me2Si group (→ 23). Removal of the Et3Si group (→ 24) and coupling afforded the homooctamer 26 and the heterooctamer 25. Yields of iodination, silylation, and desilylation were consistently high, while heterocoupling proceeded in only 50–55%. Cleavage of the (i‐Pr)3SiC and MeOCH2O groups of 11 (→ 27), 15 (→ 28), 20 (→ 29) and 26 (→ 30) proceeded in high yields (Scheme 3). Complete deprotection in two steps of the heterocoupling products 16 (→ 31 → 32), 19 (→ 33 → 34), and 25 (→ 35 → 36) gave the unprotected dimer 32, tetramer 34, and octamer 36 in high yields (Scheme 4). Only the dimer 32 is soluble in H2O; the 1H‐NMR spectra of 32, 34, and 36 in (D6)DMSO (relatively low concentration) show no signs of association.
From Colchicine and Some of Its Derivatives to 1,2,3,9,10‐Pentamethoxybenzo[a]heptalenes
Authors: Kouroupis Pavlos , Hansen Hans‐Jürgen 
Published: December 2004

AbstractA two‐step synthesis of 4‐methylcolchicine (13), starting from colchicine (2), has been developed (Scheme 5). In three steps, 4‐ethylcolchicine (28) is also accessible from 2 (Scheme 8). Colchicine (2) and its derivatives 13 and 28 have been transformed into the benzo[a]heptalene derivatives 9, 18, and 34, respectively, by Hofmann degradation of the corresponding deacetylcolchiceine 3, 19, and 29, respectively, followed by methylation of the two O‐functions first with diazomethane and then with trimethoxonium tetrafluoroborate (Scheme 2 and 6). The thus formed tropylium salts gave, on deprotonation with Me3N in CHCl3, the expected pentamethoxybenzo[a]heptalenes 9, 18, and 34, respectively. X‐Ray crystal‐structure analysis of 9 (Fig.3) and 18 (Fig. 7), determination of the vicinal coupling constants of the H‐atoms at the heptalene skeleton as well as the measurement of the racemization rate of the new benzo[a]heptalenes revealed a marked influence of the substituent at C(4) on the degree of twisting of the heptalene skeleton. The absolute configuration of the resolved heptalenes was deduced from their long‐wavelength CD maxima around 350 nm. The heptalenes with a negative maximum in this range possess (7aP)‐configuration.
1,3‐Dipole mit zentralem S‐Atom aus der Umsetzung von Aziden mit Thiocarbonyl‐Verbindungen: Eine unerwartete MeS‐Wanderung im Abfangprodukt eines ‘Thiocarbonyl‐aminids’ mit Dithiobenzoesäure‐methylester
Authors: Mlostoń Grzegorz , Romański Jaroslaw , Linden Anthony , Heimgartner Heinz 
Published: December 2004

1,3‐Dipoles with a Central S‐Atom from the Reaction of Azides and Thiocarbonyl Compounds: An Unexpected MeS Migration in the Trapping Product of a ‘Thiocarbonyl‐aminide’ with Methyl DithiobenzoateReaction of PhN3 with O‐methyl thiobenzoate (11a) and thioacetate (11c) as well as with the dithio esters 11b,d at 80° yields the corresponding imidates and thioimidates 12 (Scheme 3). The formation of 12 is rationalized by a 1,3‐dipolar cycloaddition of the azide and the CS group followed by successive elimination of N2 and S. In the three‐component reaction of 11b, PhN3, and the sterically crowded thioketone 1a, 1,2,4‐trithiolane 13a and 1,4,2‐dithiazolidine 3a are formed in addition to 12b (Scheme 4). The heterocycles 13a and 3a are trapping products of 1a and ‘thiocarbonyl‐thiolate’ 5a and ‘thiocarbonyl‐aminide’ 2a (ArPh), respectively (Scheme 6). These 1,3‐dipoles are formed as reactive intermediates. Surprisingly, in the presence of catalytic amounts of acids, the major product is the (methyldithio)cyclobutyl thioimidate of type 14 (Scheme 5), formed by an acid‐catalyzed MeS migration in dithiazolidine 17. A reaction mechanism is proposed in Scheme 7.
Synthesis of a Type‐VIβ‐Turn Peptide Mimetic and Its Incorporation into a High‐Affinity Somatostatin Receptor Ligand
Authors: Gramberg Dieter , Weber Christoph , Beeli Reto , Inglis Janice , Bruns Christian , Robinson John A. 
Published: December 2004

AbstractThe synthesis of a cis‐Phe‐Pro dipeptide mimetic is described, which adopts a type‐VIβ‐turn conformation. In this mimetic, the α‐positions of Phe and Pro are joined by a CH2CH2 bridge, thereby forming a fused bicyclic system, and fixing a geometry similar to that seen in cis‐Phe‐Pro units in protein crystal structures. The dipeptide mimetic 20 was synthesized in optically pure form starting from (R)‐α‐allylproline (6; Schemes 1, 3, and 4), with a free carboxylic acid and an Fmoc‐protected N‐terminus, thereby allowing its incorporation into linear and cyclic peptides using standard solid‐phase methods. The mimetic 20 was incorporated into the cyclic somatostatin analogue cyclo(‐Phe = Pro‐Phe‐D‐Trp‐Lys‐Thr‐), where Phe = Pro represents the mimetic. This analogue shows a high affinity (pIC50 8.6) for somatostatin receptors on rat‐brain cortex membranes. Based on NMR studies in aqueous solution, likely low‐energy conformations for this analogue were deduced using restrained dynamic simulated annealing. The conformations found, which include a distorted type‐II′ turn at D‐Trp‐Lys, are similar to low‐energy conformations deduced elsewhere for cyclo(‐Phe‐Pro‐Phe‐D‐Trp‐Lys‐Thr‐), as well as to those seen in crystal structures of the somatostatin analogue octreotide.
Molecular Magnetism and Iron(II) Spin‐State Equilibrium as Structural Probes in Heterodinuclear d–f Complexes
Authors: Piguet Claude , Rivara‐Minten Elisabeth , Hopfgartner Gérard , Bünzli Jean‐Claude G. 
Published: December 2004

AbstractFe(ClO4)2 reacts with the segmental ligand 2‐{6‐[1‐(3,5‐dimethoxybenzyl)‐1H‐benzimidazol‐2‐yl]pyridin‐2‐yl}‐1,1′‐dimethyl‐5,5′‐methylene‐2′‐(5‐methylpyridin‐2‐yl)bis[1H‐benzimidazole] (L2) in MeCN to give the diamagnetic deep violet complex [Fe(L2)2]2+ where the metal is pseudo‐octahedrally coordinated by two perpendicular tridentate binding units. When L2 reacts with an equimolar mixture of Ln(ClO4)3 (Ln = La, Ce, Pr, Nd, Sm, Eu) and Fe(ClO4)2, electrospray‐mass spectrometric, spectrophotometric, and 1H‐NMR data in MeCN show the selective formation of the deep red heterodinuclear C3‐cylindrical complexes [LnFe(L2)3]5+ where the three ligands L2 are wrapped about the metal‐metal axis. FeII occupies the pseudo‐octahedral capping site produced by the three bidentate units and LnIII lies in the resulting ‘facial’ pseudo‐tricapped trigonal prismatic site defined by the three remaining tridentate coordinating units. The heterodinuclear complexes [LnFe(L2)3]5+ display spin‐state equilibrium (1A ⇄ 5T) and thermochromism in MeCN between 243 and 333 K. Detailed 1H‐NMR, UV/VIS, and magnetic measurements in solution show that the partial spin‐crossover behavior of [LnFe(L2)3]5+ occurs for Ln = LaEu with similar thermodynamic parameters (ΔHsc = 20–23 kJ·mol−1 and ΔSsc = 55–66 J·mol−1·K−1) indicating that the size of LnIII has a negligible influence on the spin‐state equilibrium. However, the smaller LnIII ions have less affinity for the pseudo‐tricapped trigonal prismatic coordination site in the heterodinuclear complexes as demonstrated by the partial decomplexation of [YFe(L2)3]5+ to give [Fe(L2)2]2+ and the absence of the heterodinuclear complex [LuFe(L2)3]5+ under the same conditions. The crucial role played by the sterically demanding FeII in the assembly processes is discussed together with the use of the efficient combination of lanthanide probes with magnetic d‐block probes for the design and investigation of luminescent and magnetic materials with controlled structural and physical properties. Photophysical measurements reveal that efficient ligand → metal and Eu → Fe energy transfer occur in [EuFe(L2)3]5+ which strongly quench both the ligand and the Eu‐centered luminescence.