The advancement in high-performance electronic devices demands low cost, robust, and non-volatile memory components. The research in the field of electronics and switches has put credence in molecular systems for their usage in various devices, involving the design and characterization of molecular materials having exciting physical properties. The ability to fine-tune the physical properties (optical, electronic, magnetic and structural) with mild external stimuli such as light, temperature, pressure, magnetic and electric field, etc. makes these systems feasible for technological applications. One of the synthetic advantages of well-known cyanido-based precursors is the predictability of the geometries and properties of the resulting self-assembled architectures. With a rational choice of cyanido-based building blocks, various moleculebased polymetallic coordination clusters and networks have been synthesized. The ambidentate cyanide ligand stabilizes numerous oxidation states of transition-metal units and can form a linear bridge between metal centers. Lowdimensional heterobimetallic complexes with varying structures and topologies have been achieved using tailored cyanometallate building blocks. These systems can exhibit fascinating physical properties, such as behaving as Single-Molecule Magnets (SMMs) , Single-Chain Magnets (SCMs) , or exhibiting Spin Crossover (SCO) and Metal-to-Metal Electron-Transfer (MMET) , etc. Increasing interest in iron-cobalt photomagnetic Prussian Blue Analogues (PBAs) following the investigation by Hashimoto et al., scientists have been motivated to broaden the class of PBAs and investigate the origin of MMET properties deeply. The reversible interconversion of the diamagnetic [Fe II LS(S=0)- Co III LS(S=0)] and paramagnetic [Fe III LS(S=1/2)-Co II HS(S=3/2)] pairs in Fe/Co PBAs could be triggered by light or thermal variations. The electronic properties of the {FeLS II/III -CN-CoLS/HS III/II } pair precisely depends upon the linearity of the bridging cyanide linkers and the redox potential difference between the donor and acceptor units. These parameters can be finetuned by controlling the coordination sphere of the metal ions by a rational choice of the building blocks and capping ligands on both sides of the cyanide bridge to promote the reversible photo-and thermo-induced MMET between the {FeLS II/III -CN-CoLS/HS III/II } pair near ambient temperature. Herein, the syntheses, crystal structures, optical, magnetic, and photomagnetic properties of two cyanide-bridged heterobimetallic 1D coordination networks with repeating {Fe-CN-Co} units are reported. Treatment of (TBA)[Fe (2). The purity and thermal stability of 1 and 2 have been determined by elemental analysis and thermogravimetric analysis (TGA). 1 is stable up to 340 K, and a gradual weight loss between 340 -400 K (ca. 4%) (Fig. , ESI), corresponding to the release of one acetonitrile molecule as interstitial solvents is observed, whose presence is confirmed by single-crystal structure analysis (vide infra). 2 undergoes weight loss between 330 -365 K (ca. 4%) before decomposition, corresponding to the release of one acetonitrile molecule as an interstitial solvent. Single crystal X-ray diffraction analyses were performed at 85 K (1) and 200 K (2) (Fig. , S2-S8; Tables , ESI). 1 crystallizes in the orthorhombic Pbca space group, while the orthorhombic P212121 space group was observed for 2. In both compounds, similar surroundings for iron and cobalt centers were observed Please do not adjust margins Please do not adjust margins and bridged consecutively by cyanide group give rise to a cationic {[Fe(Tp)(CN)3][Co(vim)4]} + repeating unit forming a 1D chain with zig-zag and wave like appearance (Fig. ), in 1 and 2 respectively. Both cationic chains have tetrafluoroborate as counter anion and different lattice solvent molecules. One water and one acetonitrile molecule were present as crystallizing solvent molecules in 1, while 2 has one acetonitrile molecule in the structure. The coordination geometry around each iron center is best defined as slightly distorted octahedron with FeC3N3 surrounding using Continuous Shape Measures (CShM) analysis (Table , ESI), in which the iron center is coordinated to the three nitrogen donor atoms of the Tp ─ ligand and three carbon donor atoms of two bridging and one terminal cyanide ligand. Each cobalt center is in a distorted octahedral geometry coordinated by four nitrogen donor atoms from vim ligand, and two nitrogen from two bridging cyanide ligands, which occupy the trans-positions (Table , ESI) matches well with the CShM analysis. The Fe-C bond lengths are in the range of 1.837(8)-1.901(9) Å (for 1) and 1.870(7)-1.920(9) Å (for 2), whereas the Fe-N bond lengths are lying in the range of 1.995(6)-2.004(6) Å (for 1) and 2.007(6)-2.027(7) Å (for 2) respectively (Table , ESI), which are in agreement with the LS Fe(II) ion in a FeC3N3 distorted octahedral coordination environment. The average Co-N bond lengths in 1 and 2 are 1.913(6) Å and 1.926(3) Å respectively (Table , ESI), lying in the range expected for the LS Co(III) ions in a CoN6 distorted octahedral coordination environment. All these results indicate {Fe II LS-CN-Co III LS} moieties in 1 and 2 at measured temperatures. The cyanidobridged Fe-CN angles are almost linear in 1 (177.7(6)°) and (171.05(4)°) (Table , ESI). In contrast, a significant difference is observed in cyanido-bridged Co-NC angle and hence the Fe-CN-Co bridging unit, which is largely deviated from the linearity in 2 with a value of 157.13(3)°, while this angle is 173.8(6)° in 1 (Table For 2, peaks at 2090 cm -1 and 2049 cm -1 correspond to CN of bridging cyanide in {Fe II LS-CN-Co III LS} and free terminal cyanide in Fe II LS-CN group, respectively. In addition, the peaks at 2486 cm - 1 and 2490 cm -1 in 1 and 2 respectively are ascribed to the B-H stretching coming from the Tp ─ ligand on the Fe(II) building block unit. The presence of four characteristic peaks in the range 1040 -1105 cm -1 indicates the presence of BF4 -counter anion in 1 and 2. The broad band at 3415 cm -1 in 1 corresponds to the presence of O-H stretch coming from water of crystallisation and stretching vibration at 2250 cm -1 in 1 and 2 signifies the presence of acetonitrile in the crystal structure. UV/vis/NIR spectroscopic measurements were performed in solid and in solution state for 1 and 2 at room temperature (Figs. ). Both compounds showed two broad band centered at around 430 nm and 630 nm which correspond to a metal-toligand charge transfer (MLCT) transition (Fe II LS → cyanide) and a metal-to-metal charge transfer (MMCT) transition from Fe II LS→Co III LS unit, respectively. The temperature-dependent magnetic susceptibility measurements were performed on polycrystalline samples in the temperature range of 2 -300 K at 10000 Oe (Fig. , ESI) external magnetic field. At 300 K, for both 1 and 2, the measured T ( is magnetic susceptibility equal to M/H; where, M=magnetization and H = external magnetic field) value is close to 0 cm 3 mol -1 K, which remains constant upon lowering the temperature down to 2 K, confirming the presence of diamagnetic {Fe II LS(S=0)-Co III LS(S=0)} unit in the entire experimental range (Fig. , ESI) for both 1 and 2. Solid-state optical reflectivity measurements for 1 and 2 were carried out in the temperature range of 10 -280 K to study the evolution of absolute reflectivity as a function of temperature (Figs. 2, S16 -S17, ESI), where no significant changes were observed for both compounds apart from the slight changes in absolute reflectivity due to temperature variation of the sample. Both compounds were cooled in the dark down to 10 K and optical response was studied before and after irradiation with white light at 10 K. For 1, the spectrum resulting upon Please do not adjust margins Please do not adjust margins irradiation of the sample with white light (0.4 mW/cm 2 ) for 30 minutes shows a significant change in the absolute reflectivity ca. 500 nm and also in the range of 650 nm to 890 nm than the spectra obtained in the dark at 10 K and 280 K (Fig. ) indicating the probability of photo-induced electron transfer and thus the formation of metastable paramagnetic {Fe III LS-CN-Co II HS} state from the diamagnetic {Fe II LS-CN-Co III LS} ground state. However, for 2, the spectra recorded at 10 K in the dark and after irradiation of the sample with white light (0.4 mW/cm 2 ) for 30 minutes perfectly overlapped (Fig. ), ruling out the possibility of photo-induced electron transfer in 2. For 1, the evolution of absolute reflectivity as a function of time was studied under white light irradiation at 10 K, and the saturation effect was observed after irradiation ca. 200 min (Fig. ). The evolution of absolute reflectivity at 780 nm shows a rise in the absolute reflectivity value, reaching a saturation value of 0.66 after 200 min of irradiation, on the other hand, evaluation of absolute reflectivity at 532 nm leads to a fall in the absolute reflectivity value from 0.42 to 0.32 (Figs. 2, S19, S21, ESI). Thermal stability of the photo-induced state was studied by heating the sample after reaching the saturation value with white light irradiation, which showed a decrease in the absolute reflectivity value due to the thermal relaxation of the photoinduced metastable state. A complete relaxation was observed at 88 K (T relax ) (Fig. , ESI), further confirmed by photomagnetic measurements (vide infra). The absolute reflectivity data obtained beyond this temperature exhibited the same behavior as in the dark. In addition to the above experiments, a set of 14 LEDs (385 nm to 1050 nm) were used to conduct the photoexcitation experiments at 10 K to find the most efficient wavelength for irradiation for the photomagnetic measurement (Figs. S22 -S23, ESI). All 14 LEDs show some increase in the absolute reflectivity value for 1, in agreement with the white light's efficiency, where the maximum efficiency was observed for the 830 nm region. The LED irradiations induced changes were plotted as the difference of absolute reflectivity (ΔAR) at 780 nm (Fig. ). This set of data shows the most efficient irradiations for 1 lie in the 780 -940 nm range. The photo-induced electron transfer in 1 was explored further by the photomagnetic studies at 10 K using 830 nm laser light (4 mW/cm 2 ). Under 830 nm laser light irradiation, the T value at 10 K increases rapidly and attains a value of 3.66 cm 3 mol -1 K after 12 h (Fig. and). This value lies close to the expected value for {Fe III LS(S=1/2, g = 2.6)-Co II HS(S = 3/2, g = 2.45)} with significant orbital contribution, thereby signifying the transformation of diamagnetic {Fe II LS-CN-Co III LS} state to photoinduced metastable paramagnetic {Fe III LS-CN-Co II HS} state. In dark, upon increasing the temperature from 2 K -10 K (sweep rate 0.4 K min -1 ), measured T value raised from 2.0 cm 3 K mol -1 to 3.66 cm 3 K mol -1 which could be ascribed due the Spinorbit coupling, magnetic anisotropy coming from the Co II and Fe III pairs of Fe III LS-Co II HS unit and/or intermolecular antiferromagnetic interactions. With increasing the temperature from 10 K -60 K, T values decrease slightly to reach a plateau with a value of 2.78 cm 3 K mol -1 . Upon further increasing the temperature, the photo-induced paramagnetic metastable state relaxes back to the thermodynamic diamagnetic ground state at 80 K consistent with optical reflectivity studies (vide supra).