21.15109/CONCORDA/VF4I94Papp, MariannMariannPapp0000-0003-4553-5167Wigner Research Centre for PhysicsKeszthelyi, TamásTamásKeszthelyi0000-0002-4223-6594Wigner Research Centre for PhysicsVancza, AndorAndorVancza0000-0001-8449-0796Wigner Research Centre for PhysicsBajnóczi, G. ÉvaG. ÉvaBajnóczi0000-0002-8469-5887Wigner Research Centre for PhysicsKováts, ÉvaÉvaKováts0000-0002-8358-857XWigner Research Centre for PhysicsNémeth, ZoltánZoltánNémeth0000-0002-4399-1890Wigner Research Centre for PhysicsBogdán, CsillaCsillaBogdánWigner Research Centre for PhysicsBazsó, GáborGáborBazsóWigner Research Centre for PhysicsRozgonyi, TamásTamásRozgonyi0000-0001-9519-7739Wigner Research Centre for PhysicsVankó, GyörgyGyörgyVankó0000-0002-3095-6551Wigner Research Centre for PhysicsARP2023ChemistryPhysicsOptimized molecular geometriesOptimized molecular energiesSchemes on the synthesis of the ligandsNMR spectraMössbauer spectraCyclic VoltammetryBuzsaki, DanielDanielBuzsakiWigner Research Centre for Physics2023-10-102023-11-0810.1021/acs.inorgchem.3c0027110.26434/chemrxiv-2022-4645x1182919510331640238960760360760560760358920413117874023896076036076066066055882031212133271213327118944023983923926076026076066076045892030719830321983032118346737231640238939239260560660560860358821332118934023896066066046086035892030916040301604030118184708431640238939139160660360660860258820309799319458621621377158754840141031219401410324814014772694401397821440123068351331449401415949554014110255540141234227401484720040149886114014314174127135640141606530401459598440141439060401485641740149966414014296646244256445502128977455050617045501057872454911382174549339585150021345505094594550514927454910681854549114785845493307831369113455021037931386164441245501148419454912966314549322828text/plainapplication/pdftext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plainchemical/x-cifchemical/x-ciftext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plainchemical/x-cifchemical/x-ciftext/plainapplication/pdftext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plainchemical/x-cifchemical/x-ciftext/plainapplication/pdftext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plaintext/plainapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-streamchemical/x-xyzapplication/octet-stream1.0CC BY 4.0The properties of transition-metal complexes and their chemical dynamics can be effectively modified with ligand substitutions, and theory can be a great aid to such molecular engineering. In this paper, we first theoretically explored how substitution with a Cl atom at different positions of the terpyridine ligand affects the electronic structure of the [Fe(terpy)₂]²⁺ complex. We found that besides the substitution at position 4′, the next most promising candidate to cause substantial electronic effects is that where the side pyridine ring is substituted at position 5 (β). Therefore, next, we examined in detail the Fe(II) complexes of the 5-chloro and 5,5″-dichloro derivatives of terpy, theoretically and experimentally, to reveal how these substitutions modify the ground state properties and the lifetime of the excited quintet state in such complexes. In addition, we extend the investigation to the complexes of the analogously substituted derivatives of 4′-SMe-terpy. The substitution at position(s) 5 (and 5″) with Cl lowers the energy of the quintet state and increases its lifetime; the results on the 4′-SMe-substituted complexes show similar changes with these two substitutions, verifying that these effects are more or less additive. This study contributes to the enhancement of our molecular engineering toolset for modifying the potential energy landscape of similar complexes.Government of Hungary and the European Regional Development FundVEKOP-2.3.2-16-2017-00015National Research, Development and Innovation Fund of Hungary (NKFIH)2018-1.2.1-NKP-2018-00012National Research, Development and Innovation Fund of Hungary (NKFIH)FK 124460National Research, Development and Innovation Fund of Hungary (NKFIH)PD 131845