•A mononuclear iron(II) spin crossover complex was synthesized.•Thermal and light induced spin crossover was achieved.•An incomplete spin crossover was observed.A mononuclear complex {Fe(L)2[N(CN)2]2} (1) has been synthesized through the reaction of (naphth-1-yl)-N-(3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine (L) with Fe[N(CN)2]2. Magnetic measurement reveals that 1 exhibits a thermal induced one-step spin crossover behavior with transition temperature T1/2 of 75 K. Furthermore, the light induced excited spin state trapping effect is observed on 1.A mononuclear spin crossover complex {Fe(L)2[N(CN)2]2} has been synthesized based on (naphth-1-yl)-N-(3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine. Thermal and light induced spin transition between the HS and the LS state was observed on Fe(II) ion.Download high-res image (147KB)Download full-size image

AbstractIt is an ongoing challenge to design and synthesize magnetic materials that undergo colossal thermal expansion and that possess potential applications as microscale or nanoscale actuators with magnetic functionality. A paramagnetic metallocyanate building block was used to construct a cyanide-bridged Fe-Co complex featuring both positive and negative colossal volumetric thermal-expansion behavior. A detailed study revealed that metal-to-metal charge transfer between 180 and 240 K induced a volumetric thermal expansion coefficient of 1498 MK−1 accompanied with hysteretic spin transition. Rotation of the magnetic building blocks induced change of π⋅⋅⋅π interactions, resulting in a negative volume expansion coefficient of −489 MK−1, and another hysteretic magnetic transition between 300 and 350 K. This work presents a strategy for incorporating both colossal positive and negative volumetric thermal expansion with shape and magnetic memory effects in a material.

AbstractIt is an ongoing challenge to design and synthesize magnetic materials that undergo colossal thermal expansion and that possess potential applications as microscale or nanoscale actuators with magnetic functionality. A paramagnetic metallocyanate building block was used to construct a cyanide-bridged Fe-Co complex featuring both positive and negative colossal volumetric thermal-expansion behavior. A detailed study revealed that metal-to-metal charge transfer between 180 and 240 K induced a volumetric thermal expansion coefficient of 1498 MK−1 accompanied with hysteretic spin transition. Rotation of the magnetic building blocks induced change of π⋅⋅⋅π interactions, resulting in a negative volume expansion coefficient of −489 MK−1, and another hysteretic magnetic transition between 300 and 350 K. This work presents a strategy for incorporating both colossal positive and negative volumetric thermal expansion with shape and magnetic memory effects in a material.

AbstractIt is a challenge to reversibly switch both magnetism and polarity using light irradiation. Herein we report a linear Fe2Co complex, whereby interconversion between FeIIILS(μ-CN)CoIIHS(μ-NC)FeIIILS (LS=low-spin, HS=high-spin) and FeIIILS(μ-CN)CoIIILS(μ-NC)FeIILS linkages could be achieved upon heating and cooling, or alternating laser irradiation at 808 and 532 nm. The electron spin arrangement and charge distribution were simultaneously tuned accompanying bidirectional metal-to-metal charge transfer, providing switchable polarity and magnetism in the complex.

•One thricyanometallate based chain {FeIII2FeII} has been synthesized.•Ferromagnetic interaction dominates in them.•The complex exhibits the coexistence of the SCM and spin-glasses behavior.A cyano-bridged ferromagnetic {FeIII2FeII} alternating chain {[FeIII(pzTp)(CN)3]2[FeII(imidazole)(H2O)]}·3H2O (1) (pzTp = tetrakis(pyrazolyl)borate) was synthesized via rational design. Crystal structure analysis studies demonstrated that complex 1 had a one-dimensional double zigzagging chain-like structure. Magnetic measurements showed that ferromagnetic interactions dominate in 1 and the AC magnetic susceptibility revealed two limit regimes in accordance with the single chain magnet and spin-glass behavior.One cyano-bridged based {FeIII2FeII} chain has been synthesized by utilizing the thricyanometallate precursors [FeIII(pzTp)(CN)3]− with the Fe2 + ion and imidazole as an auxiliary ligand. The complex exhibits the coexistence of the single chain magnet and spin-glass behavior.

•A tetranuclear cyanide-bridged FeIII2NiII2 cluster was synthesized.•Magnetic measurements indicated that this compound displayed single-molecule magnet behavior.A tetranuclear cyanide-bridged FeIII2NiII2 cluster [FeIII(Tp)(CN)3]2NiII2(4, 4′-dibromo-2, 2′-bpy)4·2ClO4 (1) (Tp = hydrotris(pyrazolyl)borate) was synthesized. Magnetic measurements indicated that this compound displayed single-molecule magnet behavior with the pre-exponential factor of τ0 = 1.79(8) × 10− 10 s and the relaxation energy barrier of Δ/kB = 65.1(9) K.A tetranuclear cyanide-bridged FeIII2NiII2 cluster [FeIII(Tp)(CN)3]2NiII2(4, 4′-dibromo-2, 2′-bpy)4·2ClO4 (1) (Tp = hydrotris(pyrazolyl)borate) was synthesized. Magnetic measurements indicated that this compound displayed single-molecule magnet behavior.

A cyanide-bridged FeIII2CoII double zigzag chain, {[FeIII(bipy)(CN)4]2CoII(btab)2}n [bipy=2,2′-bipyridine, btab=4,4′-(1,3-phenylene)-bis-4H-1,2,4-triazole] (1), was obtained with tetracyanometalate precursors and CoII ions. The chains were further linked by the ditopic btab ligands to a layer. Magnetic property studies demonstrate that 1 shows both metamagnetism with a critical field Hc=400 Oe and single-chain magnet behavior.

With the coordination geometry of DyIII being relatively fixed, oxygen and sulfur atoms were used to replace one porphyrin pyrrole nitrogen atom of sandwich complex [(Bu)4N][DyIII(Pc)(TBPP)] [Pc = dianion of phthalocyanine, TBPP = 5,10,15,20-tetrakis[(4-tert-butyl)phenyl]porphyrin]. The energy barrier of the compounds was enhanced three times, with the order of DyIII(Pc)(STBPP) > DyIII(Pc)(OTBPP) > [(Bu)4N][DyIII(Pc)(TBPP)] [STBPP = monoanion of 5,10,15,20-(4-tert-butyl)phenyl-21-thiaporphyrin, OTBPP = monoanion of 5,10,15,20-(4-tert-butyl)phenyl-21-oxaporphyrin]. Theoretical calculations offer reasonable explanations of such a significant enhancement. The energy barrier of 194 K for DyIII(Pc)(STBPP) represents the highest one among all the bis(tetrapyrrole) dysprosium SMMs, providing a strategy to rationally enhance the anisotropy and energy barrier via atom replacement.

The metal–organic framework {[Fe(2,2′-bipyridine)(CN)4]2Co(4,4′-bipyridine)}·4H2O (Fe2Co-MOF) with single-chain magnetism undergoes an intermetallic charge transfer that converts the Fe2Co charge/spin configurations from Fe3+LS–Co2+HS–Fe3+LS to Fe2+LS–Co3+LS–Fe3+LS (LS = low spin, HS = high spin) around 220 K under ambient pressure. A series of coherent phase transitions in structure, magnetism, permittivity and ferroelectricity are found to take place accompanying with the charge transfer, making Fe2Co-MOF a unique ferroelectric single-chain magnet at low temperature. Moreover, our detailed measurements of magnetization, dielectric constant, and Raman scattering under high pressures illustrate that the charge transfer as well as the resulting multifunctional transitions can be readily induced to occur at room temperature by applying a tiny external pressure of about 0.5 kbar. The present study thus provides a pressure well-controllable multifunctional material with potential applications in a broad temperature region across room temperature.

The present study describes the designed synthesis, X-ray structures, and magnetic properties of two 2D cyano bridged heterobimetallic WV–CoII networks, {[W(CN)8]2[Co(phpy)4]3}·2CH3OH·2H2O (1) and {[W(CN)8]2[Co(4-spy)4]3}·6H2O (2) (phpy = 4-phenylpyridine, 4-spy = 4-styrylpyridine). Both compounds consist of cyano-bridged 12-metal 36-membered ring units, Co6W6(CN)12, joined by organic linkers into a 2D plane. The layer presents a corrugated configuration in compound 1 and a plane configuration in compound 2 due to different π–π stacking interactions. Magnetic measurements reveal that both 1 and 2 have a transition to the spin glass-like phase due to competitive magnetic interactions.

It is a challenge to synthesize a porous tubular coordination polymer with magnetic properties. Utilizing [FeII(bipy)(CN)4]2− (bipy = 2,2′-bipyridine) as the building block to react with Mn2+, we successfully synthesized a cyano-bridged tubular coordination polymer with dominant ferromagnetic interactions. The inner surface of the heterometallic tube is hydrophilic, whereas the outer surface is hydrophobic. The framework is stable up to 320 °C and can adsorb N2 and CO2. The ferromagnetic interactions were transmitted via the diamagnetic N–C–FeII–C–N species between Mn2+ ions in the tube.

One trinuclear and two tetranuclear cyanide-bridged FeIII–NiII complexes were synthesized via treatment of a tricyanometallate with divalent Ni salts in the presence of 1-butylimidazole, 2,2-bipyrimidyl and 1,10-phenanthroline, respectively. Magnetic property studies demonstrated that the three complexes exhibit single-molecule magnet behavior as a result of strong intracluster ferromagnetic coupling and weak intercluster magnetic interactions.

Herein, we report the investigation of a mononuclear spin-crossover complex [FeIIL2][ClO4]2 (L = 2,6-bis{4,4-dimethyl-4,5-dihydrooxazol-2-yl}pyridine). This compound undergoes a structural phase transition around 173 K, accompanying with an abrupt spin-transition process. Interestingly, it exhibits a multi-induced spin-crossover behavior mediated by heat, light, pressure and solvent.

•Two octacyanometallate based chains {WNi} and {MoNi} have been synthesized.•Ferromagnetic interaction dominates in them.•The coupling interaction of WVNiII chain was larger than the MoVNiII chain.The preparation, single-crystal X-ray crystallography and magnetic properties are reported for two single-zigzag chain complexes {[W(CN)8][Ni(imi)4]}·Bu4N·CH3OH·2H2O (1) and {[Mo(CN)8][Ni(imi)4]}·Bu4N·2H2O (2) (imi = imidazole, Bu = normal-butyl). The structure studies reveal that both complexes feature one-dimension anion chains linked by [W(CN)8]3 − units in 1 or [Mo(CN)8]3 − units in 2. Magnetic studies show that strong ferromagnetic exchange is operative within the WV(μ-CN)NiII units for (1) and MoV(μ-CN)NiII units for (2).Two cyano-bridged based {WNi} and {MoNi} chain have been synthesized by utilizing two octacyanometallate precursors [M(CN)8]3 − (M = Mo, W) with the Ni2 +(imidazole)4 as the second building block. The ferromagnetic interaction dominates in them.

•Two new cyano-bridged {Fe4M2} hexanuclear were successfully prepared.•Strong ferromagnetic interactions exist in the two compounds.•The spin ground state are S = 5 and S = 6 for two compounds, respectively.Two hexanuclear complexes of formula [FeIII(Tp*)(CN)3]4[FeII(tptz)]2 (1), [FeIII(Tp*)(CN)3]4[CoII(tptz)]2 (2) [Tp* = hydridotris(3,5-dimethylpyrazolyl)borate, tptz = (2,4,6-tris-(2-pyridyl)1,3,5-triazine] have been synthesized via directional assembly of metallocyanate precursor and metal cationic ions. The magnetic properties characterization indicate that ferromagnetic interactions dominate in the two complexes, resulting in a spin ground state of S = 5 and S = 6, respectively.Two new hexanuclear complexes have been synthesized via rational method utilizing tricyanometalate precursor and metal cationic ions with organic ligand. The magnetic properties have been investigated in the range of temperature 2–300 K, indicating both two compounds are ferromagnetic.

•Cyano-bridged tetranuclear or chain was synthesized via rational design.•The tetranuclear cluster shows dominant ferromagnetic interaction and SMM behavior.•The zigzag chain presents dominant antiferromagnetic behavior and spin-canting.A tetranuclear cluster and an alternating zigzag chain were synthesized via rational assembly of the same cyanometalate building blocks with different Mn(III) Schiff bases possessing varying proportions of sterically hindered groups causing steric hindrances. The tetranuclear cluster [(Tp*)Fe(CN)3]2[Mn(salen)]2·H2O [1; [(Tp*)Fe(CN)3]− [Tp* = hydrotris(3,5-dimethylpyrazol-1-yl) borate], salen = N,N′-ethylenebis(salicylideneiminato) dianion] was formed with Schiff bases possessing smaller steric hindrances, whereas the one-dimensional alternating zigzag chain {[(Tp*)Fe(CN)3Mn(salcyen)]·2CH3OH·H2O}n [2; salcyen = N,N′-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion] was formed with Schiff bases possessing larger steric hindrances. Magnetic measurements revealed that 1 exhibits single-molecule-magnet behavior with dominant ferromagnetic interactions, whereas 2 exhibits spin-canting behavior with dominant antiferromagnetic interactions.One tetranuclear cluster and one alternating zigzag chain were synthesized via directional assembly of metallocyanates with Mn(III) Schiff bases possessing different steric hindrances. Magnetic measurements revealed that the tetranuclear cluster exhibits SMM behavior with dominant ferromagnetic interactions, whereas the 1D chain presents spin-canting behavior with dominant antiferromagnetic interactions.

•Two new cyano-bridged {Fe2Cu} double zigzag chains were successfully prepared.•Both chains show metamagnetic behavior.•The coexistence of metamagnetism and single-chain magnets behavior was observed.It is a challenge to tune the magnetic properties of 1D complex via balancing the intra- and interchain magnetic interactions. Utilizing tricyanometalate precursors with different steric hindrance to react with CuII in the presence of 4-styrylpyridine or 4-cyanopyridine, respectively, two cyano-bridged {Fe2Cu} double-zigzag chains [FeIII(Tp)(CN)3]2CuII(4-styrylpyridine)2·3CH3CN·3H2O (Tp = hydrotris(pyrazolyl)borate) (1) and [FeIII(pzTp)(CN)3]2CuII(4-cyanopyridine)2·2CH3CN·H2O (pzTp = tetrakis(pyrazolyl)borate) (2) were obtained. 1 shows metamagnetism with a critical field of 700 Oe, whereas 2 shows the coexistence of metamagnetism and single-chain magnet behavior.Utilizing cyanometalate building blocks with different steric hindrance to tune interchain magnetic interactions, two new cyano-bridged {Fe2Cu} double-zigzag chains were successfully synthesized. The change from metamagnetism to the coexistence of metamagnetism and single-chain magnet behavior was realized.

A cyano-bridged ferromagnetic {FeIIINiII} alternating chain {[Fe(pzTp)(CN)3][Ni(chxn)2]}·ClO4·H2O (1) (pzTp = tetrakis(pyrazolyl)borate, chxn = (1R,2R)-1,2-diaminocyclohexane) was synthesized via rational design. Crystal structure analysis and magnetic studies demonstrated that compound 1 had a one-dimensional zigzagging chain-like structure and slow magnetic relaxation.

The reaction of tricyanometallate precursor, (Bu4N)[(pzTp)Fe(CN)3] (pzTp = tetrakis(pyrazolyl)borate) with Cu(ClO4)2·6H2O in the presence of the monodentate 4-styrylpyridine ligand afford one novel one-dimensional (1D) heterobimetallic cyano-bridged chain, [Fe(pzTp)(CN)3]2Cu(4-styrylpyridine)2•2H2O•4CH3OH (1). The molecular structure was determined by single-crystal X-ray diffraction. In compound 1, the FeIII ion is coordinated by three cyanide carbon atoms and three nitrogen atoms of pzTp anions. Whereas, the CuII ion is surrounded by four cyanide nitrogen atoms and two nitrogen atoms from two monodentate 4-styrylpyridine ligands. Magnetic measurements indicate that compound 1 exhibits intrachain ferromagnetic coupling and single-chain magnets behavior.The reaction of tricyanometallate precursor with CuII in the presence of the monodentate 4-styrylpyridine ligand affords one novel one-dimensional (1D) heterobimetallic cyano-bridged chain complexes of squares. Magnetic measurements indicate that compound 1 exhibits intrachain ferromagnetic coupling and single-chain magnets behavior.Highlights► One cyano-bridged {Fe2Cu} chain has been synthesized via rational design. ► Strong ferromagnetic interactions exist between the FeIII and CuII ions. ► The compound exhibited single chain magnet behavior.

The reaction of tricyanometallate precursor, (Bu4N)[(Tp*)Fe(CN)3] (Tp* = hydrotris(3,5-dimethylpyrazol-l-yl)borate) with Co(ClO4)2·6H2O in the presence of the bidentate dpa (dpa = 2,2′-dipyridyl amine) ligand affords one novel cyano-bridged heterobimetallic {Fe2Co2} molecular square, [FeIII(Tp*)(CN)3]2[CoII(dpa)2]2•2ClO4•4H2O•4CH3OH (1). The molecular structure was determined by single-crystal X-ray diffraction. In compound 1, FeIII ion is coordinated by three cyanide carbon atoms and three nitrogen atoms of Tp* anions. Whereas, the CoII ion is surrounded by two cyanide nitrogen atoms and four nitrogen atoms from two bidentate dpa ligands. Cyclic voltammetry (CV) measurements showed that complex 1 exhibited one quasi-reversible waves (0.1 V vs SCE) in the reduction process, and irreversible waves in the oxidation process. Magnetic measurements indicate that complex 1 exhibits a strong intramolecular ferromagnetic interaction between the low-spin FeIII(S = 1/2) and high-spin CoII(S = 3/2) ions.The reaction of tricyanometallate precursor with CoII in the presence of the bidentate dpa ligand afford one novel cyano-bridged heterobimetallic {Fe2Co2} molecular square. Ferromagnetic properties existed between the metal ions. In addition, the cyclic voltammetry (CV) and magnetic properties of the compound have also been investigated.Highlights► One cyano-bridged {Fe2Co2} molecular square has been synthesized via rational design. ► Strong ferromagnetic interactions exist between the FeIII and CoII ions. ► The compound exhibited quasi-reversible waves in the reduction process. ► The compound exhibited irreversible waves in the oxidation process.

Using Bu4N[Fe(Tp*)(CN)3]− (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) as the building block to react with CuII and N-methylimidazole, we obtained a one-dimensional (1D) heterobimetallic cyano-bridged chain, [Fe(Tp*)(CN)3]2Cu(N-methylimidazole)2·2H2O (1). The crystal structures and magnetic studies demonstrate that complex 1 exhibits slow relaxation of the magnetization due to strong intrachain ferromagnetic coupling and weak interchain interactions.

•A tetranuclear FeIII2CoII2 cluster and a hexanuclear cluster FeIII4CoII2 were synthesized.•Antiferromagnetic to ferromagnetic coupling were achieved.A tetranuclear cluster {[(Tp)Fe(CN)3]Co(pp)H2O}2·[(Tp)Fe(CN)3]2 ⋅ 6H2O (1; Tp = hydrotris(pyrazoly)borate, pp = 2,6-bis(N-pyrazolyl)pyridine) and a hexanuclear cluster {[(pzTp)Fe(CN)3]2Co(pp)}2·2H2O (2; pzTp = tetrakis(pyrazoly)borate) have been synthesized via rational assembly of the same (ppCoII)2 + unit and different tricyanometalate building blocks with varying proportions of sterically hindered groups. Magnetic measurements reveal that 1 exhibits the dominant antiferromagnetic interactions between Fe(III) and Co(II) ions, while 2 exhibits the dominant ferromagnetic interactions.From a tetranuclear Fe2Co2 cluster to a hexanuclear Fe4Co2 cluster was synthesized based on different cyanometalate building blocks with varying proportions of sterically hindered groups. The corresponding magnetic properties change from antiferromagnetic interaction to ferromagnetic interaction.

Herein, we investigate the spin transition properties in a series of mononuclear Fe(II) complexes constructed by two pybox ligands and four counter anions. 1(BF4) undergoes an abrupt spin-transition at around 150 K, which proceeds to 50% completeness and is accompanied by a structural phase transition. 1(BPh4)·MeCN, 2(ClO4), and 2(BF4) all display gradual and complete SCO behaviours around or above ambient temperature. The desolvated compound 1(BPh4) exhibits a gradual but incomplete SCO. 2(PF6)·MeCN, 2(PF6) and 2(BPh4) show a two-step SCO. The well-defined two-step SCO of 2(BPh4) takes place at 100–200 K (T1/2 = 150 K) and 400–500 K (T1/2 = 446 K). In contrast, compounds 1(BF4)·MeCN, 1(PF6)·MeCN·Et2O and 1(PF6) remain high-spin at the measured temperatures. The LIESST (light induced excited spin state trapping) effect of several SCO compounds are also investigated, which display photo-conversion during light irradiation at low temperature at a relatively high level. Our results demonstrate that the [Fe(pybox)2]2+ series of complexes will become a new versatile system in spin-crossover research.

With the coordination geometry of DyIII being relatively fixed, oxygen and sulfur atoms were used to replace one porphyrin pyrrole nitrogen atom of sandwich complex [(Bu)4N][DyIII(Pc)(TBPP)] [Pc = dianion of phthalocyanine, TBPP = 5,10,15,20-tetrakis[(4-tert-butyl)phenyl]porphyrin]. The energy barrier of the compounds was enhanced three times, with the order of DyIII(Pc)(STBPP) > DyIII(Pc)(OTBPP) > [(Bu)4N][DyIII(Pc)(TBPP)] [STBPP = monoanion of 5,10,15,20-(4-tert-butyl)phenyl-21-thiaporphyrin, OTBPP = monoanion of 5,10,15,20-(4-tert-butyl)phenyl-21-oxaporphyrin]. Theoretical calculations offer reasonable explanations of such a significant enhancement. The energy barrier of 194 K for DyIII(Pc)(STBPP) represents the highest one among all the bis(tetrapyrrole) dysprosium SMMs, providing a strategy to rationally enhance the anisotropy and energy barrier via atom replacement.

It is a challenge to synthesize a porous tubular coordination polymer with magnetic properties. Utilizing [FeII(bipy)(CN)4]2− (bipy = 2,2′-bipyridine) as the building block to react with Mn2+, we successfully synthesized a cyano-bridged tubular coordination polymer with dominant ferromagnetic interactions. The inner surface of the heterometallic tube is hydrophilic, whereas the outer surface is hydrophobic. The framework is stable up to 320 °C and can adsorb N2 and CO2. The ferromagnetic interactions were transmitted via the diamagnetic N–C–FeII–C–N species between Mn2+ ions in the tube.

One trinuclear and two tetranuclear cyanide-bridged FeIII–NiII complexes were synthesized via treatment of a tricyanometallate with divalent Ni salts in the presence of 1-butylimidazole, 2,2-bipyrimidyl and 1,10-phenanthroline, respectively. Magnetic property studies demonstrated that the three complexes exhibit single-molecule magnet behavior as a result of strong intracluster ferromagnetic coupling and weak intercluster magnetic interactions.

The present study describes the designed synthesis, X-ray structures, and magnetic properties of two 2D cyano bridged heterobimetallic WV–CoII networks, {[W(CN)8]2[Co(phpy)4]3}·2CH3OH·2H2O (1) and {[W(CN)8]2[Co(4-spy)4]3}·6H2O (2) (phpy = 4-phenylpyridine, 4-spy = 4-styrylpyridine). Both compounds consist of cyano-bridged 12-metal 36-membered ring units, Co6W6(CN)12, joined by organic linkers into a 2D plane. The layer presents a corrugated configuration in compound 1 and a plane configuration in compound 2 due to different π–π stacking interactions. Magnetic measurements reveal that both 1 and 2 have a transition to the spin glass-like phase due to competitive magnetic interactions.

Herein, we report the investigation of a mononuclear spin-crossover complex [FeIIL2][ClO4]2 (L = 2,6-bis{4,4-dimethyl-4,5-dihydrooxazol-2-yl}pyridine). This compound undergoes a structural phase transition around 173 K, accompanying with an abrupt spin-transition process. Interestingly, it exhibits a multi-induced spin-crossover behavior mediated by heat, light, pressure and solvent.

A cyano-bridged ferromagnetic {FeIIINiII} alternating chain {[Fe(pzTp)(CN)3][Ni(chxn)2]}·ClO4·H2O (1) (pzTp = tetrakis(pyrazolyl)borate, chxn = (1R,2R)-1,2-diaminocyclohexane) was synthesized via rational design. Crystal structure analysis and magnetic studies demonstrated that compound 1 had a one-dimensional zigzagging chain-like structure and slow magnetic relaxation.

The rational design of magnetic and fluorescent bifunctional materials is attracting increasing interest. In this study, two mononuclear Fe(II) complexes, namely [Fe(L)2(NCS)2] (1) and [Fe(L)2(NCSe)2] (2) are synthesised by combining a spin-crossover unit and a fluorescent ligand (naphth-1-yl)-N-(3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine (L) to achieve bifunctionality. Single-crystal X-ray studies and magnetic measurements confirm the presence of spin crossover behaviours; these measurements agree with the results of the temperature depended Raman spectra and infrared spectra. Thermally and light-induced spin crossover is clearly observed for both complexes. The nature of the co-ligand (NCS−vs. NCSe−) shifts the transition temperature by approximately 60 K. The infrared spectra after irradiation reveal that the electronic states are ascribable to the photomagnetic effect at 10 K. Furthermore, temperature-dependent fluorescence emission spectra exhibit the coexistence of spin crossover and fluorescence for 1 and 2.